The lingering weaknesses Bottas must eliminate now

Valtteri Bottas has got what he wanted; a fourth season alongside Lewis Hamilton at Mercedes. It's a vote of confidence in him, albeit not as emphatic as a new multi-year deal would have been. So what does he need to do next season to ensure it is not just a case of one more season?

The man himself remains focused on becoming Formula 1 world champion, as you'd expect for someone who only turned 30 on Wednesday. He reiterated his determination to do that on Thursday, but Mercedes doesn't need Bottas to become world champion. His role is far more nuanced than that, and consequently almost as difficult to perform.

Bottas famously said "that hurts" when confronted with Toto Wolff's suggestion he had been a "sensational wingman" for much of last year's Hungarian Grand Prix. But that's exactly what Mercedes needs him to be. Yet the role of the unofficial number two driver is often misunderstood and there's far more to it than simply driving around and being slower than Hamilton more often than not.

Mercedes won't deliberately hold Bottas back or give him inferior equipment as that would be self-defeating, while team orders will only be used in extraordinary situations - such as in last year's Russian Grand Prix. But not upsetting the de facto team leader, in this case Hamilton, is a positive and one of the reasons why Bottas has been retained.

If Mercedes builds a strong car and gets the best out of Hamilton, it will win the drivers' championship. This means Bottas is there to contribute towards those two objectives, and assist in the delivery of the constructors' crown - as well as providing a title shot should anything go badly wrong for Hamilton.

By that definition, Bottas has been bang on the money this year. He stands second in the world championship - albeit with the caveat that he is under more pressure for that position from Max Verstappen than he should be - has picked up a couple of race wins and is helping Mercedes to the constructors' championship.

His return of 75% of Hamilton's points is more than enough for a leading team's second driver as history suggests you need your lower-scoring driver to pick up at least two-thirds of the leader's points. According to Wolff, Bottas has delivered on the demand that he produce a stronger first half of the season than he did in 2017 and '18. That's been done, no question.

His qualifying performances are also on point, beating Hamilton one-third of the time over his time at Mercedes and being, on average, within a tenth this year when slower. Measured against Hamilton, that's extremely accomplished.

Bottas must sustain, or improve on, those performances. But the more difficult question is how he tackles the weaknesses. This becomes a bigger concern the more threatening the opposition becomes.

This year, Red Bull took time to get on top of its package and Ferrari has repeatedly shot itself in the foot, so the pressure hasn't been as intense as it could be. Next year, that could be different.

If F1 produces the season everyone dreams of, but rarely gets, with the three top teams closely-matched and going at it hammer and tongs over the campaign, Bottas will be under serious pressure.

That's a small problem for qualifying, as even though he's proved he can usually be close to Hamilton there have been occasions this year when he's left a gap that was too big. If you are 0.286 seconds down, as Bottas was in France, or 0.362s behind, as he was in Germany, against stronger opposition that opens the door to having cars between him and Hamilton - as was the case at Hockenheim where Verstappen got onto the front row.

Bottas can't be expected to be right behind Hamilton every Saturday, but he needs to minimise the opportunities for Red Bull and/or Ferrari to split the Silver Arrows. But Saturdays won't be the real test of Bottas's value in 2020 and, barring regression, he should do the job well enough. Instead, it will be his race-day performances that will need to sharpen up, so his real battleground is on Sundays.

Wolff recently described tyre management as Bottas's "second weakness" to tackle, the first one being qualifying pace. Bottas has got on top of the first but must now make gains over race stints

Mercedes has finished one-two seven times in 12 races this season, twice with Bottas ahead but on average he's been 6.3s behind. That's promising, but it does mask some problems.

By his own admission, Bottas still needs to improve when it comes to tyre management. While not as big a problem this season thanks to the 2019 Pirelli tyres, there are still occasions when he's weaker in the final part of a stint compared to Hamilton having matched him early on. This is partly a question of driving style and it's one that is not easy to fix.

Bottas tends to load the tyres for a little longer than Hamilton during cornering rather than the rapid rotation Hamilton favours, which tends to make life easier when the car is tricky but accelerates thermal degradation when the car is at its best.

Also significant is that he's not the strongest when it comes to limiting the rear tyre-slip, something arch-tyre manager Sergio Perez excels at, so on track surfaces where that's at its most challenging he can be exposed.

Hamilton is an underrated manager of tyres, despite his regular 'feedback' on tyre situations over the radio, so this doesn't mean Bottas has no idea what he's doing. But there is a disadvantage. That surely played a part at Silverstone where, despite his protestations to the contrary, we can't be sure Bottas could have matched Hamilton's victorious one-stop even if the Finn had not committed to the more orthodox two-stopper. There it was the front axle that was the concern, but usually, the problem is rear tyre degradation.

That should be further ameliorated by the more robust Pirellis in the pipeline for next year, but you can't cheat physics and there will likely still be some symptoms. The end of a stint is a bad time to be vulnerable in this way.

Firstly, it leaves you more vulnerable to an undercut pass because a car behind with rubber in a better condition can often close up. Secondly, it can result in a more cautious approach to the early stages of stints. In a world where there are six top cars broadly capable of the same pace, that's a vulnerability that could result in fewer one-twos, fewer points and - even more crucially - fewer occasions when Bottas is in a position to screen Hamilton from the rest.

The Hungarian GP, where Pierre Gasly's poor performance meant there was no second Red Bull to be seen when Hamilton and Mercedes took their 'free' pitstop, illustrates how valuable the second driver can be simply by being there in broadly the right place. Bottas is significantly stronger than Gasly was at Red Bull, but there is a vulnerability there that could compromise his effectiveness.

Wolff recently described tyre management as Bottas's "second weakness" to tackle, the first one being qualifying pace. Bottas has got on top of the first but must now make gains over race stints. Interestingly, Bottas's numbers in terms of proximity to Hamilton have floated around a similar level from 2017-19.

It's a double-edged sword as a quality, because what Mercedes wants is someone who is very compliant when battling with Hamilton but with sharper teeth when fighting the rest

This year, using calculations from Forix, he's either been ahead of Hamilton or within 20s (roughly a pitstop window) of Hamilton on 80.4% of race laps. That compares to 81.4% last year and 84.6% in 2017. It's a rough-and-ready measure but shows that by and large Bottas's performance in races is strong.

He just needs to iron out the periods of weakness, such as the final few laps of a stint where he can lose ground because of tyre condition. The question is whether he can ameliorate that without losing his pace earlier in stints.

Then there's the question of wheel-to-wheel combat. Bottas is not what you might term a combative driver. It's not that he's timid, it's just that he's not a naturally aggressive character in battle.

Hungary showcased this, where he left Hamilton plenty of space on the outside of Turn 2, only to get crowded off the track by his team-mate at Turn 3. It's a weakness Nico Rosberg (pictured below battling Hamilton in 2014) had as well. Drivers who struggle with this, certainly when at this stage of their career, rarely find another level.

It's a double-edged sword as a quality, because what Mercedes really wants is someone who is very compliant when battling with Hamilton but with sharper teeth when fighting with the rest. Bottas isn't ever likely to fulfil the second part of that equation on a sustained basis.

This perhaps also explains why he can sometimes find himself stuck in races when out of position. That, combined with occasional tyre troubles, can add up to chinks in the armour that could allow a Red Bull or a Ferrari through. That can mean less protection for Hamilton, fewer points and a wingman who isn't as effective.

But it's clear that these are small problems. Bottas is also capable of winning commandingly from the front, claiming pole positions and beating top drivers, so these problems will only really weaken him in a situation where Ferrari and Red Bull are strong. This means there are three possibilities for next year.

The first is that the results are similar to this year and he continues to score a healthy percentage of the team's points, occasionally beats Hamilton, mostly follows him home and all is well.

The second is that the opposition is stronger and too often the door is prised open and he's coming home from fourth to sixth position.

There is a third eventuality, the one that Bottas will be focused on - that's the one where he proves himself capable of leading the team.

This can be subdivided into two paths - one, desperately unlikely, where he outperforms Hamilton over the season.

The second is that he's consistently strong enough that Mercedes is confident Bottas could win the championship in 2021 should out-of-contract Hamilton walk away.

The one that most likely results in Bottas being at Mercedes in 2021 and beyond is the first path, although to do that Bottas must continue to raise his game just in case Verstappen, Charles Leclerc, Sebastian Vettel and whoever is in the second Red Bull are consistent threats. That's his challenge.

His progress over the past two-and-a-half seasons suggests he can deliver, but life in a top team is never easy even for a support act. Bottas is a classy driver, fast in qualifying, able to win races, brilliant when the track is green and always strong on the less-abrasive surfaces.

But it's one other quality that will be key to ensuring an extended run with Mercedes beyond 2020: the capacity to analyse and improve against the toughest of benchmarks in Hamilton. He's got to the second half of the season in his best position yet, so has the foundation to build on.

Bottas's battle to convince Mercedes to keep him on in 2021 starts right now.