Michael Schumacher was unsure what was happening at first when his Mercedes seemed to come unstuck from the track in Canada and take up flying lessons over the chicanes. But then the Mercedes pit crew came over the radio to alert him to the problem.

"At first, I didn't know exactly what the problem was," Schumacher said later. "I overshot the corner, ran through the grass and asked myself what was going on. Then the team told me about the problem and I saw it in the mirrors."

The problem was with the Mercedes' rear wing flap, part of the car's "double DRS" (drag reduction system) system. The flap had locked in the open position, dramatically lowering the downforce available to the driver going through the corners. Since he'd had no warning, he was caught out and was lucky not to crash.

Schumacher managed to bring the car back to pit lane, where the mechanics attempted some manual adjustments on the wing - another way of saying that they tried to force the seized flap back into the closed position. But no amount of brute strength could overcome the hydrualics that were keeping it firmly open, and that meant the car couldn't go back out on track without getting black flagged for violating the DRS activation rules.

"I can only apologise to Michael for a further technical failure," said team principal Ross Brawn. "[He] suffered a hydraulic issue which left his DRS jammed open and it was not possible to fix it in race conditions."

Schumacher's Montreal race had already been compromised by getting caught in a train of cars early on while the team were asking him to take care of the supersoft tyres, and despite stopping early to try and break out of the logjam and get into clean air it simply hadn't worked for him, even before the DRS failed.

"Of course it's disappointing for all of us but it's not a question of pointing fingers; stuff like this happens," said Schumacher. "I know the team are doing their best and that it probably hits them even harder than me. We'll be back on the attack in Valencia."

It was a better day for Nico Rosberg, who challenged Mark Webber for fourth place on the opening laps but then fell foul to attacks in quick succession from Felipe Massa and Paul di Resta while he himself was being told to preserve his first set of option tyres.

"It was a mixed-up race and it was difficult to find a rhythm, particularly at the start, but by the end, the gap to the leading cars was not that big," he said. "Sixth place is a decent result today and it's important for both me and the team to keep scoring points for the championship and maintain our consistency."

"We asked both drivers to be cautious with the super soft tyres in the first five laps to ensure we didn't push them too hard," confirmed Brawn. "When we gave them the go-ahead, it was clear that Nico - who was running in clean air - was extremely quick and one of the fastest cars.

"We had a very quick car today, as Nico's performance in particular showed, but a combination of failing to achieve our potential in qualifying and a messy race cost us positions at the flag."