de la Rosa subs for Perez

Pedro de la Rosa has been drafted into the second Sauber cockpit from Friday afternoon's free practice session, taking over from Sergio Perez, who suffered a heavy crash in Monaco two weeks ago.

The Mexican had been declared fit for the event, and posted the eleventh fastest time of opening practice, but paddock speculation suggested he may have suffered a reaction to the concussion that ruled him out of the race in Monaco.

Team Lotus' engineering chief Mike Gascoyne told his Twitter followers that 'Pedro de la Rosa standing in for Perez in the Sauber for FP2 for the remainder of the event', although it was not yet clear how long the Mexican would be sidelined for.

de la Rosa drove a part-season for Sauber in 2010, before being replaced by fellow veteran Nick Heidfeld and going on to take up the German's role as development driver with Pirelli. At the end of the season, he returned to previous employer McLaren, resuming the test and development role he held for seven year, and team CEO Martin Whitmarsh was spotted in conversation with the Sauber team during the break between sessions in Montreal, prior to de la Rosa's return to the Swiss outfit.

A statement issued by the Sauber team shortly after the start of the second 90-minute practice session confirmed that Perez would be out of action for the remainder of the weekend having complained of feeling unwell during the opening session.

"Of course I wanted to drive and I had no doubt I was alright but, apparently, this is unfortunately not the case," Perez admitted, "I am deeply disappointed. I spoke to the team after the session and told them that I'm not a hundred per cent fit. I only want to drive when I'm a hundred per cent well. I need some more time to recover."

Sauber says it took the decision on the grounds of safety, suspecting the illness was almost certainly a consequence of the accident he suffered in qualifying at Monaco, but said that it hoped the Mexican would only have to miss this weekend's event, before returning in Valencia in two weeks' time.

"This development hit us by surprise, because Sergio underwent thorough medical checks, first in the hospital in Monaco, then in a hospital in Z?rich, and finally, the FIA doctors gave him the green light this Thursday in Montreal," team principal Peter Sauber commented, "Nobody could have foreseen that he would feel unwell. Maybe we are being overly cautious but, when it's about the health of our drivers, we take zero risks. We want to thank Pedro de la Rosa and McLaren for helping us out in this situation."