Mohamed Salah arrived at Liverpool's Melwood training centre on Thursday morning to undergo a scan on his groin injury sustained against Manchester City in the Champions League.
Reds boss Jurgen Klopp faces the prospect of leaving Salah, his side's star player this season, out of Saturday's Merseyside derby in a bid to ensure he is fit to face City on Tuesday.
Liverpool produced a commanding 3-0 lead in their quarter-final first leg but know they need another strong showing at the Etihad Stadium to ensure they progress to the semi-finals.