Jack Ross will carefully assess Aiden McGeady over the next couple of days but won't make any 'snap judgements' ahead of the second leg at Fratton Park.
The experienced winger, Sunderland's dangerman, had missed the last couple of games as the club manages his fractured foot injury but he was named in the starting line-up for the visit of Portsmouth to the Stadium of Light only to pull out the side mid-warm-up.
McGeady was seen running from the pitch straight down the tunnel, the news confirmed shortly afterwards that he was to be replaced in the side by Lynden Gooch.
It was a major blow for Sunderland but they managed to win the game 1-0 thanks to sub Chris Maguire's stunning second half volley.
Ahead of Thursday's second leg at Fratton Park, Ross said: "Aiden has been playing with a foot problem for a while and he has been playing with the aid of injections.
“He had a little bit longer rest period by missing the last couple of league games, he trained Thursday but for some reason the injections he has had prior to matches didn’t have quite the same effect.
“He wanted to give it as long as he could, and he took part in the warm-up, but it was still causing him a lot of pain.
“I have a duty of care to him and I wouldn’t ask him to take any more injections because he deserves a lot of credit for what he has been prepared to do in the games thus far.
“We will just see how he reacts over the next 24-48 hours.
“He needs a prolonged period of rest and he will get that over the summer, we were just hoping to get him through to that point.
“The pain has fluctuated so we won’t make any snap judgements on it.
"We will look at it again tomorrow morning and go from there.”