The bleak reality for those trying to topple Hamilton inside Mercedes

The stopwatch is the most decisive measure of performance in motorsport. That comes with a condition, however, because in isolation a single lap time means little. There needs to be context - a comparison to a simulator run or a theoretical perfect lap.

These are strong reference points for a team, but the indicator transfixing everybody else is whether or not a driver can beat their nearest rival, the one running in equal machinery. Have they have gone faster than their team-mate?

It becomes a more thankless task when you're driving alongside Lewis Hamilton, statistically the best qualifier of all time with 88 pole positions. That's been the challenge presented to Mercedes drivers Nico Rosberg and then Valtteri Bottas since Hamilton joined the team in 2013.

From the dawn of the hybrid powertrain era of Formula 1 in 2014, only once has Hamilton been eclipsed to the drivers' title. To a degree, the seeds for Rosberg's 2016 triumph were sewn at the beginning of the millennium in go-karts and took 16 years to come to fruition. What chance, then, does Bottas have after only three seasons alongside a six-time world champion?

Tony Ross, now the chief engineer of the Mercedes Formula E team, is best known for his howling team radio messages that greeted every one of Rosberg's 23 grand prix victories.

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Having started his racing career at Nissan Motorsport for its mid-1990s touring car programme, Ross moved to Williams to aid the V12 Le Mans project with BMW before legendary technical director Patrick Head called him up to the F1 team. Following stints with Juan Pablo Montoya and Nick Heidfeld, in 2006 Ross forged a fruitful partnership with Rosberg as his race engineer.

After a year apart when Rosberg left for Mercedes in 2010, Ross then followed the German to Brackley in 2011, and continued on the pitwall with Bottas - who replaced Rosberg in 2017 following his sudden decision to retire - until 2018.

Rosberg proved he could beat a multiple champion as he squared up to, and vanquished the returning Michael Schumacher in their three seasons together between 2010 and 2012. But when Hamilton joined Mercedes, the task presented was far greater. Rosberg had beaten an F1 great who was past his prime, next he needed to beat a driver in their prime.

Although Rosberg had one season's more experience in F1 than Hamilton at that point, it was the 2008 champion who had the greater experience of being in position to fight for a title thanks to his early McLaren success. For Rosberg, who had departed from a declining Williams to join a fledging Mercedes, he was facing an entirely new proposition at the very top of the pecking order.

"Lewis has progressed massively. He's not the same driver who joined Mercedes in 2013. He's grown a lot as he has just learned so much more" Tony Ross

Ross recalls: "I think at that stage [2013 to 2016], Nico and Lewis were not that dissimilar in terms of performance. But they were very different drivers in their approach: Lewis is much more of a natural driver, Nico is somebody who is able to learn a lot. He could, on the right day, sometimes beat Lewis.

"If you look at Lewis, he has progressed massively. He's not the same driver who joined Mercedes in 2013. He's grown a lot as he has just learnt so much more.

"Between him and Nico, they were learning off each other all the time. They were just ramping up their ability, and the team was learning a lot as well.

"Although we [the team on Rosberg's car] were still fighting against the other side of the garage, and it was not a particularly nice atmosphere, the engineers were still talking, and the two drivers were still learning from each other."

This two-way learning process started life when the pair first became team-mates in karting. Bottas, by stark contrast, had no pre-existing partnership with Hamilton to be aware of any deficiencies that the Brit might have.

He waded into battle having fared well against 2008 title runner-up Felipe Massa in his time at Williams, but otherwise had little experience of fighting against a champion, dicing for grand prix wins and no experience of being in a title fight since his GP3 crown in 2011.

Ross adds: "The issue with Valtteri is that when he turned up, he wasn't facing the Lewis of the time that Nico was fighting against. He was facing the Lewis that had taken another step beyond.

"Valtteri was kind of up against it from that point of view. He's learning all the time, but he's just coming from this platform where he hasn't had the background and experience that Lewis has had - that shows."

The foundation upon which Rosberg built his 2016 title triumph took shape in the closing stages of the preceding season. Hamilton claimed his third championship at Austin, and from there Rosberg won the remaining three rounds of the season.

That momentum carried across the winter break, as he earned the spoils in the first four races of the 2016 campagin. A calamitous opening lap of the Spanish Grand Prix, in which the two tangled and crashed out, permitted Red Bull debutant Max Verstappen to earn his maiden F1 triumph. It then took until round six in Monaco for Hamilton to come out on top.

"Lewis still wanted to win those races in 2015," says Ross. "He wasn't like 'I don't give a shit', but he had just won the world championship and so maybe his focus wasn't 100% there. The determination to do it was still there, though."

Mercedes continued with its powertrain-inspired performance superiority in 2016, but issues with reliability reared their head. All of the problems manifested themselves on Hamilton's car, as Rosberg enjoyed total mechanical dependability.

Hamilton was docked three-places on the grid in China as a legacy of gearbox damage sustained in Bahrain, which was then compounded by an MGU-H failure in qualifying. He suffered an ERS fault, also in qualifying, for the Russian Grand Prix.

The pair came to blows in Austria, which resulted in a broken front wing and a 10-second penalty for Rosberg as Hamilton bagged the win. Wind on to Spa, and those early-season mechanical woes required further grid penalties for Hamilton, as Mercedes swapped out components and so exceeded the allotted limits for the season.

The dramatic and fiery bearing failure for polesitter Hamilton in Malaysia remains the most memorable and visual calamity of that season. Still people argue Rosberg was fortunate in his title victory, and there's a sound case for it. But he made the best of the favourable hand he was dealt.

"The 2016 season was close," says Ross. "If you look at look at previous years, Nico had some bad luck, definitely. Lewis had some bad luck - you can't take that away from him. At the end of the day, Nico had done enough to then just finish second in the last few races.

"Obviously, Abu Dhabi was still a level above that in terms of the stress that we all went through."

"Where Lewis has gone now, he's on another level. The commitment that Nico had to achieve with a young family and everything else like that to win the title, he knew that he couldn't realistically do that again" Tony Ross

Entering the Abu Dhabi season finale, Rosberg had a 12-point buffer at the top of the standings. Hamilton was on pole and led away at the start, avoiding the clutch-related launch issues which had plagued him all season - most notably at Suzuka. Rosberg avoided any first corner skirmishes and ducked in for second place. Come lap 32 and Hamilton began backing Rosberg up to the chasing pack of Sebastian Vettel and Verstappen in bid to regain his title chances.

As Rosberg's race engineer, when Ross is asked whether or not Hamilton became the enemy in that moment, he replies: "No, I have 100% respect for Lewis. Lewis wants to win it and he's looking at every avenue he can do to win, so Nico's got to deal with it.

"Lewis had gone off into the distance and so Nico was trying to fight off losing any positions. That was really where Nico needed to make the difference - that pass on Verstappen. It was about just making sure that he made the most, at that stage, of what was available to him so he could where he was. It's difficult with Lewis, because obviously he is looking for a way to win the championship."

Ultimately Hamilton fell short, and Keke and Nico Rosberg joined Graham and Damon Hill as the only father-and-son duos ever to win the F1 drivers' championship.

Such was the dedication and drain on Rosberg for him to win the 2016 drivers' crown, he promptly announced his retirement from racing at the FIA Prize Giving Gala in Vienna on 2 December - only five days after the title showdown. Even to his closest colleagues, this was a shock revelation.

"It was still a massive surprise," recalls Ross. "It was like 'Oh my God!'. When he rang me up before the announcement, I thought 'Right, is he still at a party somewhere? Really?' It was a shock.

"But having listened to Nico explain it, I understood his decision fully. It is hard work. If you look at where Lewis has gone now, he's on another level. The commitment that Nico had to achieve with a young family and everything else like that to win the title, that's hard work. And he knew that he couldn't realistically do that again."

Rosberg's timing was perfect in many ways. He stepped away from F1 at the height of his success and created one of very few blemishes on Hamilton's record. He never gave Hamilton the option to retaliate in head-to-head competition and so, effectively, ended a 16-year rivalry with the definitive blow.

"I pushed like crazy in all directions and along with everybody who was involved, which was also my family, a lot of sacrifices," Rosberg said at the Gala.

"My wife, for example, every time I was home she understood that I needed to rest so I never did any nights, I never took care of my little daughter, I never did any difficult things.

"She was always there to support to make it as easy as possible and that's just one example of the commitment we all put into it.

"I've achieved this childhood dream and I'm not willing to do that sort of commitment again for another year and I'm not interested in coming fourth or whatever.

"I'm a fighter and I want to win. I'm not interested to do that again, I don't want to do it again."

In many ways, it was the "commitment" that Rosberg employed that makes Hamilton's achievements even more admirable.

Rosberg identified that if he had deficiencies to Hamilton on the circuit, then he needed to recover the lost ground off track. As such he gained took on a single-minded, tunnel-vision approach to come out on top. There could be no distractions.

Hamilton, meanwhile, continues to thrive by including non-curricular F1 pursuits into his life - which has allowed him to transcend his role as a driver to become a global sporting superstar.

"With Nico and Lewis, you probably have the polar extremes and Valtteri is somewhere in between in terms of his approach" Tony Ross

As Rosberg bowed out at the top, it has since been left to Bottas to take the fight to the Mercedes' number one. He's a different operator to his predecessor, picked because he was less likely to create divisions and tension in the team.

The headlines reflect that Bottas has fared worse than his predecessor in their respective stints alongside Hamilton. To date, his best effort has been second in the standings last season, but he was some 87 points in arrears of champion Hamilton. Between 2013 and 2016, Rosberg won 22 races compared to Hamilton's 32. Since 2017, Bottas has accrued seven victories in the time Hamilton has racked up 31.

"All three of them are different - Nico, Lewis and Valtteri," explains Ross. "I would say that with Nico and Lewis, you probably have the polar extremes and Valtteri is somewhere in between in terms of his approach.

"Nico goes about his business like conducting an orchestra. He's talking to the race engineer, 'I'm going to do that'. He's talking to the performance engineer, he's talking to everybody, trying to organise what he wants.

"Whereas Valtteri, he is less demanding in that respect. He knows what he wants, but he doesn't have the same kind of personality that Nico does."

Hamilton has also kept his surroundings in the team stable, having worked with race engineer Pete Bonnington since 2013. That time together has allowed the pitwall-to-car relationship to flourish. And while there have been changes to Hamilton's performance engineer, they have been internal promotions, which minimises the disruption. Ross adds:

"If you say there's a 1000 people in the team altogether, probably 980 people don't really care who wins. It's just a small number of people.

"When you're winning the manufacturers' championship, it's yours. And when you win the drivers' championship it's still a Mercedes driver as champion. But it's just that last little bit where you are 100% focused on trying to get that driver to win the championship.

"It's difficult and it's hard to know where to draw the line. You have to be a team player, Mercedes won't win if you're not a team player - if you're not sharing data, if you're not discussing. The team will only develop if you put 100% into the team."

Bottas has shown flashes in his bid to match Hamilton's level. Aping the form of Rosberg in his title-winning campaign, it was Bottas who came out of the blocks fastest in 2019 with victory in Australia.

As Ross says: "If you look at that race, Bottas takes the lead. Lewis had picked up a little bit of car damage and Valtteri goes 'Right, OK. Blimey, I'm off!'.

"It's in his mind. The momentum builds within the driver's head. If you do that in the first race of the season then you want to carry on with the same kind of approach into each race."

But as Ross has already alluded to, this was against a Hamilton who had another two years' experience and development compared to the one Rosberg faced. So much so that 2018 and 2019 rank as Hamilton's strongest seasons to date.

Hamilton swung the momentum in his favour once more with wins in Bahrain and China, conceded Baku to Bottas, and then bounced back with four consecutive victories.

"If you look at Lewis's performance in 2018, it would have been difficult for any other driver to win that championship [as Ferrari closed the gap]," Ross continues. "What he did in terms of Monza and everything else like that was exemplary.

"There's always a lot going on in each individual race. I think Valtteri is driving consistently well and on his day will match Lewis. But sometimes Lewis just has that edge.

Such is Hamilton's command, even those within Mercedes respect there's no silver bullet to beating him

"If Lewis is not 100% there, then Valtteri's there to take advantage of it. It's difficult to mentally build up that momentum because each race is different.

"You have just got to approach it and do all the same thing. You need to keep the same kind of motions and then you'll do it. If you suddenly change things then we'll miss something and you'll lose the momentum."

This is the principle upon which any basic science experiment is built. You only change one variable at a time so you can isolate the cause of any differences in results. But it also sends out an ominous message. Such is Hamilton's command, even those within Mercedes respect there's no silver bullet to beating him.

Adding to that struggle, the team is now undeniably built around its star driver - a change in balance permitted by Rosberg's exit. For Bottas, that makes for an uninspiring ask: keep things the same, but just be better than Hamilton.