Sauber has confirmed that Nick Heidfeld will replace Pedro de la Rosa as one of its race drivers for the rest of the season.

Rumours of the swap circulated the Monza paddock on Sunday evening, but Peter Sauber refused to comment. However, starting at the Singapore Grand Prix, Nick Heidfeld will take de la Rosa's place alongside Kamui Kobayashi.

"It was a hard decision for me to make as a team principal and I want to thank Pedro for his professionalism," said team boss Sauber. "By signing Nick we have a driver we know extremely well who will help us to further judge the comparative potential of our car."

Heidfled has driven for the team in its different guises for seven seasons of his 11-year career. He started 2010 as a reserve driver for Mercedes before taking on a testing role with 2011 tyre supplier Pirelli, which undoubtedly raised his stock as he is the only experienced driver to test the new rubber.

"I'm looking forward like crazy to having the opportunity to go racing again in a good car in Formula One from the Singapore Grand Prix onwards," said Heidfeld. "After the last months I'm even more motivated than ever. For me it is like coming home, as I raced for seven years in total for the team from Hinwil. Without doubt I will be feeling at home straight away and this should help me to familiarise myself as soon as possible with the car. I want to thank Peter Sauber for the faith he has put in me."

Pedro de la Rosa is a logical replacement for Heidfled in the Pirelli testing role and said he was still hoping to return to the sport next year.

"I am surprised by the team's decision, but I respect it and would like to wish everyone good luck for the remainder of the season. I still intend to be in Formula One for 2011," he said.