McLaren Modify MP4-20 for Wurz

Wurz was forced to sit on the sidelines during the early running of McLaren's 2005 challenger because his 1.86m frame was too tall to fit into the early versions of the chassis that had been produced.

This meant the Austrian had to focus on tyre development work in the MP4-19B during the pre-season build-up, while de la Rosa worked on readying the MP4-20.

The problems fitting Wurz into the car meant that de la Rosa was the automatic choice to run McLaren's third car on Friday for the start of the season.

This is why he has subsequently been drafted in to replace the injured Juan Pablo Montoya at this weekend's Bahrain Grand Prix even though Wurz is the team's official reserve driver.

But with modifications having been made to the MP4-20 chassis so Wurz can be accommodated, he will now likely be drafted in for some of the Friday duties at Grands Prix once he is fully up to speed with the new car. His testing programme with the new car kicks off in earnest at Barcelona next week, after his first running in the car at Bahrain.

A statement from McLaren on Wednesday said: "Following the Bahrain Grand Prix, Alex will commence his testing programme with the MP4-20, and will be able to share the test driver duties with Pedro at future races."