The striker will undergo a scan on a tight hamstring on Monday with manager Derek McInnes admitting he was “touch and go” for the second leg at Pittodrie.
Aberdeen need to overturn a 2-0 first-leg defeat and have a Betfred Cup last-16 tie against Dundee to follow on Sunday. Cosgrove, who has scored eight of Aberdeen’s 13 goals this season, could miss both games. His absence was certainly felt on Sunday as Aberdeen toiled in front of goal while losing 1-0 to St Mirren.
“He’s a tightness in his hamstring,” said McInnes. “He reported it yesterday and we tried to give him every chance but he just felt it was becoming more of an issue and we decided not to bring him with us. He stayed and got treatment in Aberdeen.
“He’ll get scanned tomorrow and I think he is touch and go for Thursday. Clearly, any team would miss someone in Sam’s form. I hope he’s going to be OK for Thursday, but at this stage, it’s not clear yet.”
Curtis Main deputised against St Mirren in his first start for the club since signing from Motherwell. But he found the going tough against Jim Goodwin’s team, who took the lead through Ilkay Durmus in the 13th minute.
Aberdeen had a chance at the end when Niall McGinn slammed a shot against the post and McInnes was disappointed to have a penalty appeal waved away in the second half after the ball struck Ryan Flynn’s hand in the box from a Ryan Hedges cross. The manager accused referee Steven McLean of making his own rules up.
“It was a penalty with last year’s rules and it’s even more of a penalty with the new rules that we were told about at the referees’ meeting two weeks ago,” he said. “Steven McLean gave me his take on it. It’s obviously different [to] mine and also different to what we were told at that meeting. I think there was enough distance for that to be a clear penalty and a clear handball.”
But McInnes added: “It was not just about that. Everything was a bit safe and a bit pedantic in the first half in terms of our build up.
“I thought the way we approached the second half was far more what was needed in terms of more aggression, more speed; asking the question more. Unfortunately we never quite managed to get an equaliser.”
St Mirren manager Jim Goodwin stressed that no-one should question his side’s mettle. After being knocked out of the Betfred Cup and losing to Hibs last weekend in their league opener there was a degree of pressure on him and his team yesterday.
“Somebody said a few weeks ago that we are soft,” he said. “But I think the boys have shown that they are anything but soft.
“It was terrible conditions today and Aberdeen are a very good team and a very physical team. They put the balls in your box all the time and we had to stand up and be counted. But each and every one of my players did that. To a man we were excellent. There was not one player had a below-par performance today.”
He agreed his side had been fortunate not to concede a penalty, but said the rub of the green was “the least we deserve for what we put into the game”.