British and Irish Lions centre Jamie Roberts faces a nervous wait for the results of a scan on a hamstring after he was injured playing in the Lions 17-47 victory over the Waratahs.
The British and Irish Lions play their first Test against the Wallabies next Saturday and Roberts hopes of playing in the first Test now hang in the balance.
The Wales and Cardiff Blues midfielder failed to complete the game when he limped off 10 minutes from the end of the 47-17 win over the Super Rugby outfit to remain unbeaten on their current tour.
Roberts, who recently qualified as a doctor from Cardiff University, looked crestfallen as he was treated on the sideline by team medics just a week out from the first Test against the Wallabies in Brisbane.
Head coach Warren Gatland said a scan on Sunday will decide Roberts' fate.
"He's going to get a scan tomorrow. The medics thought it might have been a hamstring, but he said he has never pulled a hamstring before," Gatland said.
"He's not kind of sure, so he's got his fingers crossed that it may not be that. So we just have to see what happens tomorrow."
Roberts, who has played 53 internationals for Wales, is rated as the most damaging running midfielder in the northern hemisphere and he faces stiff competition for his Test spot from Brian O'Driscoll and Manu Tuilagi.
He formed a formidable centre partnership with O'Driscoll on the Lions 2009 tour of South Africa and was named the Lions' player of the series after superb performances in the first two Tests against the Springboks.
His injury may open the door for Welsh compatriot Jonathan Davies, who was outstanding in Saturday's win over the Waratahs.