Felipe Massa is currently driving better than at any other point in his Formula 1 career and is still improving, according to Williams performance chief Rob Smedley.
The Brazilian, who made his F1 debut in 2002 with Sauber, finished fifth in the Chinese Grand Prix, one place ahead of team-mate Valtteri Bottas.
After challenging for the title in 2008, ultimately finishing runner-up to Lewis Hamilton, Massa struggled to repeat that form during the next five years with Ferrari, where he worked with Smedley.
But since joining Williams last season, the Brazilian has appeared rejuvenated and his consistency this season sees him sit fourth in the drivers' championship.
Massa described the weekend in China as "fantastic", including a "perfect lap" in qualifying, and Smedley agreed: "I think that he had a very good weekend to be honest. He was right on it.
"I have worked with him for many years and I am still seeing him develop and it's good to see.
"That's a lad with 10 years-plus experience of driving Formula 1 cars, who is still able to develop and get better and better."
Smedley said that Massa seems very comfortable at Williams and has shown impressive skill in working with the tyres.
"I think one of the biggest changes that I have seen in Felipe over the last year-and-a-half is not only where he has got his head to - so he's very comfortable with himself and with his surroundings now - but I think technically how he is managing the tyres is really, really impressive," said Smedley.
"He knows what to do with the tyres, he knows what corrective action to take.
"He knows how to get them working in qualifying and he knows how to make them last in the race as good as any particular car will allow him to do.
"What we are seeing at the minute is definitely the best Felipe Massa that we have seen, definitely as good as 2008."