Broken back to keep Ralf out for season.

Ralf Schumacher could have to face spending the rest of the Formula One season on the sidelines after checks on his injured back revealed two spinal fractures.

The German, who crashed heavily in the opening laps if the United States Grand Prix, will now definitely miss this weekend's French round, although Williams-BMW has yet to confirm the news or name a replacement. Marc Gene remains favourite to partner Juan Montoya at Magny-Cours, but another driver may be sought for the longer term.

A spokesman for Schumacher confirmed the diagnosis late last night, and revealed that doctors in spa town of Bad Nauheim, where the driver is receiving treatment, reckoned that Schumacher would need as much as three months to recover to a sufficient level to contemplate getting back into an F1 car. That would mean missing all but the season-closing Japanese and Brazilian grands prix in October, and Williams may decide to cut its losses and draft in a permanent replacement for the remainder of the season. Schumacher is already believed to have agreed a deal to join the Toyota team for 2005.

The news broke on the eve of Ralf's 29th birthday, and capped what has generally been perceived as a poor season for the German and his team.

"The diagnosis is a hammer blow," Schumacher admitted to German newspaper Die Bild, "The injury is worse than we originally feared, but there is nothing I can do now but try to get through it. I am already looking forward to the moment where I can sit in the car again."

Doctors have warned Schumacher against rushing his comeback, in case he actually makes the injury worse - either by over-training or becoming involved in another accident on his return. Insiders at Williams have questioned whether the driver ever fully recovered from the concussion and bruising he received in testing for last year's Italian Grand Prix, although Schumacher insisted that he was suffering no after effects of what turned out to be a violent roll into the gravel trap at Monza.

Test driver Gene replaced the German at short notice the last time he had to stand down - taking over after Friday's free practice sessions had been completed - and went on to score an unlapped fifth place in the Italian race. The 30-year old Spaniard remains the most likely substitute for this weekend's French GP but, with the realisation that its regular pilot will miss most - if not all - of the season, Williams and BMW may cast around for a more established long-term replacement.

Former world champion Jacques Villeneuve has already been mentioned - and denied - as a possible stand-in for Magny-Cours, but it is feasible that the team could bring forward an oft-rumoured summer test in order to get the Canadian on board for Silverstone and beyond. It could also seek to prise Mark Webber out of his Jaguar contract ahead of schedule. Williams is believed to have lined the Aussie up for 2005, and a financial inducement may pave the way for an early move. Second test driver Antonio Pizzonia remains the other 'obvious' substitute.

Confirmation of Schumacher's condition will also add strength to FIA president Max Mosley's claims that Formula One is now too fast for its own good, and put further pressure on the ten teams to come up with a solution for next season - before the president forces through his own revisions on the grounds of safety.