Kurtis joins Byrne on Brno injury list.

Tomorrow's Czech Grand Prix grid will be two riders short following the news that both Aprilia's Shane Byrne and Proton KR's Kurtis Roberts have been forced to withdraw due to injury.

Byrne has been ruled out after dislocating his left wrist during a huge highside (top pics) in this morning's free practice session, in which the reigning British Superbike champion also suffered a small fracture in his left wrist, concussion and multiple cuts and bruises.

After being the given all-clear to leave hospital, the 27-year-old is expected to return to the track later this evening for further checks with GP doctor Claudio Costa, where a decision will be taken on whether an operation on the wrist is required.

However, Aprilia state that Byrne's wrist injury will also force him to miss the Portuguese Grand Prix, at Estoril in two weeks time, and the Briton remains doubtful for the Japanese Grand Prix on September 19. The team expect to make an announcement in the next few days about whether Byrne will be replaced in Portugal.

Meanwhile, Roberts will miss out on exploiting his career best 14th qualifying position after sustaining injuries a few hours after Bryne, in the wet final qualifying session. The American suffered left elbow and wrist fractures in a heavy fall but, while he will miss Sunday's race, is expected to be fit for the Portuguese GP.

"It was wetter than yesterday and I was trying to take it easy, but I had no grip," recalled Roberts. "I kept losing the rear, both into and out of the turns. Then on one lap, on the way into a turn, it went all the way to the steering lock stops, and flicked me off the highside. And I got beat up. We need some improvement in grip - there was no explanation of why it happened. The telemetry showed I was actually a little slower there than on the previous two laps."