Yet another engine problem for Red Bull

Saturday morning at Spa may have been the final nail in the coffin of Red Bull's Renault relationship, with Mark Webber retiring from the practice session with what is believed to be an engine problem.

After Sebastian Vettel's two failures at Valencia, his Australian teammate pulled into the pits at the cool but dry Belgian circuit with an evil-sounding engine note, and the early suggestion is that he will need the French V8 to be changed prior to qualifying.

Red Bull's RB5 was considered the stand-out favourite for victory this weekend, but Webber failed to set a time in the pre-qualifying practice hour, and Vettel's programme remained limited to just 14 laps.

Force India's Giancarlo Fisichella struck and killed a small animal with his front wing during the session, while Luca Badoer avoided his usual ignominy of the slowest lap time -- that dishonour went instead to Williams' Kazuki Nakajima.