De la Rosa had 10-minute warning

With Perez having complained of feeling sick after the first session in Canada, Sauber drafted in McLaren reserve de la Rosa for the remainder of the Montreal event.

And although there had been contact between Sauber and McLaren earlier in the week about de la Rosa being on standby in case Perez had any complications caused by his Monaco GP crash, the final call only came at lunch time on Friday.

"I was finishing lunch when Monisha Kaltenborn [Sauber CEO] showed up at McLaren and asked me, 'are you ready? It's very likely you will have to get in the car'," explained de la Rosa. "I checked my watch and it was ten to two and I said 'but there's 10 minutes to the start of the session!'

"From then it was a crazy race to get my helmet, my overalls, my things at McLaren, sit in the car, and set up the pedals where I wanted. But we couldn't do it, and we had to go out with the pedals where they were. But you don't have to be nervous. It's an opportunity and we have to enjoy it."

De la Rosa said he had arrived in Canada aware that Sauber could need him, but was sure that Perez was fit enough to race.

"Martin Whitmarsh had told me that Sauber had called in case there was a chance, but told me not to get carried away. So I arrived here thinking it was impossible. I knew Sergio was fine and I was sure I wouldn't get in the car, until ten to two."

As part of the contingency plan for de la Rosa, Sauber had one of the Spaniard's seats from last year - which he said was crucial to him being able to get in the car.

"We could use my seat from last year which was absolutely very, very important and vital," he said. "As far as all the rest is concerned, I went out with my McLaren overalls, boots, helmet. We also did a quick fix on the ear pieces to match the system from Sauber."

Although Sauber hopes that using the experienced de la Rosa will help its chances of scoring points, he is keeping his ambitions in check.

"Let's be realistic. I have a lot to learn yet. I need a lot more discipline with the buttons, the KERS, the DRS, because I'm used to a car with the buttons on the opposite side.

"So I have to look at the buttons and then push it. It doesn't came naturally yet. We'll be fine. I have to improve step by step, but I'm happy because I didn't expect it."