Ross Brawn insists Formula One has yet to see the best from Jenson Button despite his third victory in four races this season at the Bahrain Grand Prix.

And the boss of Brawn GP admitted he did not realise how good the Briton was until watching him take a comfortable victory.

Button had struggled in qualifying due to the heat of the Sakhir Circuit and started the race in fourth place. But he moved into the lead at the first round of pit stops, thanks predominantly to getting the better of defending world champion Lewis Hamilton in a pulsating first-lap tussle.

Brawn was full of the admiration for the 29-year-old, insisting he was more than capable of winning this season's world title.

“He's actually getting better as a driver and I think there's still more to come from him,” said Brawn. “He was exceptional and there were flashes of brilliance behind the wheel. Guys on the team have been telling me for a while how good he is and we saw that today but I don't think we've seen the best of him.

“There's no question he's good enough to be world champion but it's sadly not entirely up to him. That's going to be determined by the car and it's up to us to ensure we give him a car to keep him out front.”

The grid could undergo a massive shake-up at the next race, the Spanish Grand Prix on 10 May, with the majority of teams expected to unveil significant changes to their cars.

Brawn warned that doubts over the team's future in the build-up to the season after Honda's decision to quit F1 could be a decisive factor over whether they can sustain a championship assault for Button.

“The worry is that with the uncertainty at the start of the season, we lost some really valuable time to work on those upgrades and that could cost us big for the rest of the season,” he said.

“It's quite simple that we have to improve the car and I think we've got some good upgrades coming up but I can't second guess what the other teams are doing. We'll have to wait and see.”

Brawn described Button's display as the perfect race. After his early battle with Hamilton for third place, the Briton pulled away and set about reeling in the Toyotas of pole sitter Jarno Trulli and Timo Glock.

Button's heavier fuel load enabled him to pull out a sufficient advantage following his first stop and he was never troubled for the rest of the race.

Describing conditions as “like a sauna — the toughest I've known”, he labelled the win his best of 2009 but admitted his race pace had taken him by surprise. “The other teams seemed to have caught up and I thought Red Bull were going to have the better of us in the race so that makes this even more pleasing,” he said. “It didn't seem to be a circuit that particularly suited us so to bag another win is remarkable.

“Passing Lewis made my race. He is very difficult to overtake but on the first lap he made a few mistakes and I got him. That was the key.”

Hamilton, meanwhile, was delighted to finish fourth but said he did not expect such a strong result in Barcelona in a fortnight's time, insisting the high-downforce nature of the circuit did not suit the current car.

McLaren are expected to take steps forward for the European part of the season but Hamilton said that if Brawn GP showed greater improvements come Barcelona then everyone else could wave goodbye to the championship.

“It's going to be virtually impossible to catch them for the rest of the season if they improve their downforce on their car any more in Spain,” he said. “It was incredible how their car stuck to the track here.

“Our car, in contrast, struggled. It's certainly better than it was but I'd still say we're down by as much as 15 per cent in terms of downforce from last season's car. Technically, it's not bad but I wouldn't say it's good just yet.”