Jenson Button and Lewis Hamilton did little to dispel the belief that McLaren could have an advantage in the Chinese Grand Prix, but their performance in opening practice was overshadowed by a frightening crash suffered by Toro Rosso's Sebastien Buemi.

Having seen his team-mate set the early pace, Button vaulted to the top of the times midway through the 90-minute session, clocking a 1min 36.677secs benchmark that would not be beaten thereafter, but the closing minutes of the morning outing were dominated by, first, shock and, then, explanation, of the incident involving Buemi.

The Swiss driver had missed much of the session with brake problems on his STR5, and had only completed five timed laps when, approaching the hairpin with ten minutes remaining, he had both front wheels fly off the car amid a shower of carbon fibre. Initial replays proved inconclusive, save to magnify the severity of the failure, but team sources later revealed that they believed a new upright to have been to blame, the right-side failure of which placed intolerable strain on the entire front end assembly. Fortunately, Buemi was able extract himself from the remains of his car and return to the pits.

Unsurprisingly, he was the slowest of the established teams' drivers setting a lap, sitting in 17th overall, just ahead of the two Lotus drivers, but still fared better than Ferrari's Fernando Alonso, who failed to set a time after the engine in his F10 failed in spectacular fashion. The unit, which replaced the one lost in the closing stages of the Malaysian Grand Prix, was the unit previously substituted out of the Ferrari after qualifying in Bahrain, emphasising the Scuderia's wisdom ahead of a race Alonso went on to win.

At the opposite end of the times, the session proved to be something of a Mercedes benefit, with Button and Hamilton split by 'works' driver Nico Rosberg, with Michael Schumacher in fourth. Eight tenths of a second covered the top four, with Sepang winner Sebastian Vettel next up for Red Bull Racing, the only other driver within a second of the ultimate pace.

Renault duo Robert Kubica and Vitaly Petrov took sixth and seventh, ahead of Mark Webber, Adrian Sutil and Felipe Massa, with another 90 minutes of running scheduled for this afternoon.