Felipe Massa's performances at the end of the 2014 Formula 1 season show he is back to his very best, according to Williams performance chief Rob Smedley.
Massa endured a difficult end to his stint at Ferrari in 2013, finishing on the podium just once during his final season at Maranello.
After moving to Williams this year, Massa improved that tally to three, and second place in the season-closing Abu Dhabi Grand Prix represented his best result in F1 since the 2012 Japanese GP.
Smedley, who worked closely with Massa at Ferrari before also joining Williams for this season, said his driver's performance at Yas Marina - where he came within three seconds of denying Lewis Hamilton victory - was "flawless".
"When I first turned up [at Williams] and saw how relaxed he was in this environment, I knew that we could start to get the results that he should be getting," Smedley explained.
"And I think that has just been compounded as the year has gone on, and as he has enjoyed the environment more he has got better and better.
"I think in Abu Dhabi you saw the very best Felipe. He was absolutely flawless; he didn't put a foot wrong, there was lots of information coming back, he was involved in the strategy.
"I asked his race engineer to get him involved in that final tyre call [where Massa switched to super-soft tyres], he gave him all the information and he said 'let's go for it'.
"That's what a top driver does. A top driver gets involved and he leads from the front.
"And not only that, he was absolutely flawless: the in- and out-laps, everything, and that's the best Felipe."
Although Massa is now 33 and 2014 was his 12th season on the F1 grid, Smedley believes there is "no limit" to what he can still achieve in the rest of his career if he can maintain his current form.
"The Felipe I know can drive like that, and we have to get him and his team-mate to a level where they are doing that every weekend," said Smedley.
"If we do that, and deliver the car, then there are no limits [to what they can achieve]."