Ferrari [Images] kept Brazilian Rubens Barrichello off the track for Saturday's opening practice at the Bahrain Grand Prix after having to rebuild his new car's gearbox.

The Formula One world champions, who have gambled on racing the new F2005 in Bahrain after a poor start to the season with a modified old car, were forced to play safe at the desert circuit.

While seven-times world champion Michael Schumacher [Images] fired off a quick lap right at the end of the day's first 45-minute session to top the timesheets, Barrichello was last and the only driver without a time.

"We have repaired the gearbox but it is a temporary measure and we want to save it for qualifying," said a Ferrari spokesman.

"He won't run in the second session either."

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Ferrari, short of parts for the new car, are flying a new gearbox out from Italy [Images] which will arrive only after first qualifying.

Renault's championship leader Fernando Alonso [Images] was second quickest in the session, 1.259 seconds slower than Schumacher's lap of one minute 30.552 seconds.

The times meant little however with the leading contenders all waiting until the closing minutes before hitting the track.

McLaren's Pedro de la Rosa, the Spanish driver standing in for injured Colombian Juan Pablo Montoya [Images], was third on the timesheets while Finnish team mate Kimi Raikkonen [Images] was 19th.

Schumacher, winner of the inaugural Bahrain race last year, has just two points after two races this season.

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