The driver every Formula E team should try to sign

There's a fanciful idea that if, and it remains an if, Mercedes was to join Formula E it would offer retired Formula 1 world champion Nico Rosberg a neat way back into racing. Rosberg shocked everyone when he decided to quit after finally beating Mercedes team-mate Lewis Hamilton to the 2016 crown.

Rosberg's kept himself on the periphery since - a race appearance here, a Goodwood Festival of Speed doughnut there. After a lifetime of racing, though, he must miss it; as Hamilton said recently: "I can't even imagine how Nico's dealing with it."

What the electric single-seater series lacks in speed, especially compared to F1, it more than makes up for with close, hard racing on tight, bumpy street tracks with difficult, heavy, complex cars. Rosberg built a reputation, and a world championship assault, on being a cerebral driver. He's smart, he's quick, he's dedicated - in short, he's perfect for Formula E.

So, the Silver Arrows joins Formula E, and ROS returns to our timing screens. A nice idea, but with all due respect to the 32-year-old, if Mercedes enters the Formula E fray there's another ROS who should be top of its list. And he's already in the series.

Rosberg might be a good option in theory, but Felix Rosenqvist is the exciting reality. And not just for a hypothetical Mercedes entry - he's the driver every manufacturer already in the series should be after.

In the unpredictable world of Formula E the one thing you could be sure of, for more than a year, was Renault e.dams or Abt Audi Sport would win. You'd put your money on Sebastien Buemi or Lucas di Grassi to do the business.

Maybe Sam Bird would sneak a pole, or Jean-Eric Vergne would be on the podium. But since Formula E's inception Buemi and di Grassi have marked themselves out as the real stars.

Before last month's Berlin double-header, 12 straight races had been won (on the road at least) by either Renault or Abt/Audi. Then Rosenqvist beat di Grassi in the Saturday Tempelhof race - claiming the Mahindra team's first win in the process - and took a pole-to-flag win ahead of Buemi on Sunday. A time penalty dropped Rosenqvist to second, but Buemi's point post-race was honest and accurate: "I'm not sure I would have managed to overtake him."

Buemi and di Grassi are about the only two drivers in Formula E who could claim to be 'consistent' - and keep in mind that Buemi's spun away a good result once this season, while di Grassi has made qualifying errors and had his own in-race dramas too. But they are the standard bearers in a series that regularly catches out top-line drivers.

The nuances of Formula E make it a tricky series to dive into and succeed - just ask Oliver Rowland, who struggled in Punta del Este on a one-off at the end of his 2015 Formula Renault 3.5 title-winning year, or Jaguar's Adam Carroll, who has not gelled with the I-Type 1 at all.

The same cannot be said for Rosenqvist. He was extremely fast in pre-season testing, and was on the limit immediately in Hong Kong - launching his M3Electro into the air over a violent chicane kerb in qualifying on his 170kW run to see how much he could get away with at 200kW. He has explored the limits early on - including a silly spin in the race that day in Hong Kong while chasing team-mate Nick Heidfeld - but reined himself in very quickly.

The speed has remained, but the errors have been massively reduced. Rear-ending Oliver Turvey in Monaco during practice, caught out by the slowing NextEV driver approaching a yellow-flag zone, was a rare blot on his copybook. The rest has been impressive, and winning was a serious sign he has moved onto the top level.

Mahindra's improvement this season has put Rosenqvist in the frame in three races (Marrakech and the Berlin double-header), and he performed extremely well every time. In Marrakech he claimed pole but was overcome by Buemi and then Bird in the race as the team struggled with efficiency, particularly in his second car.

Those lessons were learned in Berlin, where circumstances aligned to present Rosenqvist with another chance to win. On Saturday there were no mistakes. There was a feeling beforehand the race could mix up the formbook because of the Tempelhof airfield surface, which was mostly concrete, abrasive, bumpy and dusty. Championship leader Buemi called it "a completely different kind of racing here".

While Michelin's new-for-2016/17 tyre meant there was not a repeat of the mass degradation seen two years ago, it was pushed to the limit. The circuit's surface and layout, revised for 2017, and high temperatures put two key factors into play: the tyres were worked harder and efficiency was key.

As it was much easier to get the tyres up to temperature initially, the kind-on-its-tyres Mahindra was immediately into the working window - alleviating a key tyre warm-up issue that has hurt it in other, cooler places such as Paris. Rosenqvist used this to very good effect over one lap, qualifying third on Saturday and taking pole on Sunday.

The race would be a different factor altogether, though. With two long and two medium-length straights energy usage was at a premium, and very warm temperatures also produced the need to manage the packages gently to prevent the battery from overheating. Thermal management was di Grassi's Achilles' heel on the Saturday, as he lamented rising battery temperatures that caused him to lose the ability to harvest energy - which assists with braking as well as recovering juice - at the end of both stints. Poor efficiency took the DS Virgin cars of Bird and Jose Maria Lopez, plus Vergne's Techeetah entry, out of the running.

Rosenqvist hit the sweet spot though, and drove at near-perfection to win both races on the road with a masterclass in race management. What was such a shame was his haste to rejoin in his second car on Sunday, which released him almost into his pitting team-mate Heidfeld and prompted the time penalty that handed Buemi the win.

That may point to hot-headedness, but if it was then this was an isolated incident because Rosenqvist has learned to blend intelligence with his speed and improving racecraft. This is a key trait in Formula E and it's also the reason Buemi wasn't sure he'd pass Rosenqvist on track for the win had he not backed off once he learned of the race leader's penalty.

"The first stint I expected him to do a big comeback and I was saving a lot of energy, more than I was planning to, just to make sure the last couple of laps would be good," said Rosenqvist.

"I had some small lock-up where he closed a bit but the last lap I was never really under pressure. In the second stint it was the same: he had the one lap where he used Fanboost, used a lot of energy to get close, and had to recover a bit.

"He slowed down because he knew I had a penalty but our race was made after he used the Fanboost, we could have held him there."

That shows an awareness and understanding of how to plan a race ahead of time and then react in the moment to execute it. While the jury's not quite reached its verdict on whether he's a Buemi/di Grassi just yet, it's only a matter of time - and Berlin has accelerated the process rapidly.

"That's something that is very special," Rosenqvist said of his victory. "Macau has always been my special one, but this comes right after. It's one of the biggest days in my career.

"To beat big teams like Renault and Abt as a bit of an underdog is a dream for every driver."

Rosenqvist said his first win "changes a lot", including the perception of him into a driver who is a proven race winner who can do the business now - not one with the potential to become that.

It's been difficult for other race winners, such as Antonio Felix da Costa or Bird, to establish themselves as a constant threat for victories. A big part is down to the quality of their equipment - and while Mahindra's own gains have been impressive, establishing itself as a regular threat for victories will be a big challenge. Keep in mind that Jaguar's second season of Formula E should be a considerable step up from its current form, BMW's Andretti tie-up will only continue to grow and NextEV's resurgence from last season to this has been clear to see.

Mahindra is believed to have Rosenqvist tied down for 2017/18 - certainly team principal Dilbagh Gill doesn't appear concerned about his driver's immediate future - but if there's a sniff of his availability teams should be falling over one another trying to get to him. And if Mahindra keeps him for another year, then what happens beyond that will be a defining factor in future championship battles. The stakes are only getting higher in Formula E and any weakness will be exploited.

Rosenqvist is a potent weapon any serious manufacturer will be eyeing up. There's little certainty in Formula E, but of his title credentials there already appears little doubt.