Ben Spies will miss his second MotoGP race in succession after withdrawing from Sunday's Malaysian Grand Prix at Sepang.
The Factory Yamaha sustained a concussion and tore soft tissue around the rib area when he crashed during qualifying for last weekend's Australia GP, preventing participation in that race.
The Texan then struggled with his injuries on Friday at Sepang and crashed twice on Saturday, including in qualifying, when he set a lap time quicker than only replacement team-mate Katsuyuki Nakasuga.
Nakasuga is standing in for 2010 world champion Jorge Lorenzo, who needed plastic surgery for a finger injury at Phillip Island.
Speaking immediately after Saturday's qualifying session, a sore Spies insisted he intended to try and race, in order to protect his fifth place in the championship.
But following consultation with Yamaha management it was jointly decided that the risk of further injury was too great and that Spies should miss not only the race, but Monday's private test session (for 1000cc bikes) at Sepang.
Spies, 17 points ahead of Gresini's Marco Simoncelli in the championship standings, now has two weeks' to recover before the Valencia season finale and official post-race test.