The Waratahs will be sweating over the injury of Wallaby utility back Berrick Barnes, following their one-point (26-27) loss to the Cheetahs.
The Tahs' key playmaker, Barnes, left the field midway through the first half after a dislocated thumb in a tackle on a Cheetahs player and watched the rest of the match from the sidelines.
He will go for scans to determine the full extent of the injury.
"It went back in, obviously, so we'll just see," a dejected coach Michael Cheika said in his post-match reaction.
"We won't know for at least 48 hours. We've got to wait."
Making his first appearance of the season after missing the opening month of the competition with a knee injury, Barnes appeared to get hurt while making a try-saving tackle on giant Cheetahs lock Lodewyk de Jager in the 17th minute.
Cheika also bemoaned his team's poor execution, which cost them several try-scoring opportunities.
Despite conceding an early lead, the home side strung together a series of clinical attacking raids to take a lead into half-time for the first time this season.
But poor execution in the dying stages of the match proved the difference, with Dave Dennis's men left missing several crucial opportunities in the narrow defeat.
Cheika lamented his team's inability to execute at key moments, saying: "It was very frustrating because it's not a game where we laid down or we didn't work hard - because we actually worked hard - but we made some poor errors of judgment at poor times and they were able to capitalise."
Dennis agreed, admitting his side's error rate proved the difference in the match.
"Those small errors hurt us, we kicked some balls away and I think that was consistent throughout the whole game," the captain said.
"We gave ourselves opportunities to win it or score points and those small errors let us down."
Cheika also conceded the team would need to improve the mental components of their play, looking ahead to the game next Sunday against the Blues.
"We've talked a fair bit around the self belief of the team after a few hard years and that's a battle we'll have to get through. We've got to have the resolve to say we're going to fight our way out of this and become better."
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