Strike duo Dirk Kuyt and David N'Gog are involved in a race against time to make Liverpool's Europa League semi-final against Atletico Madrid on Thursday.
The Reds are already without the services of leading scorer Fernando Torres for the semi-final second leg against his former club following season-ending knee surgery last week.
Kuyt suffered a calf injury during Sunday's 4-0 win at Burnley while N'Gog missed the trip to Turf Moor with a back complaint.
Both frontmen could now miss the second leg of the European tie at Anfield in what would be a major blow to the Reds' hopes of reaching next month's final in Hamburg.
"Kuyt did not train on Tuesday and will have a light session today," manager Rafael Benitez told the club's official website.
"We will decide tomorrow because he still has some problems.
"He is a really important player for us but we will not take any risks with him if it is not necessary.
"N'Gog has the same situation with his back. We will have to push him more in training today and then see how he feels tomorrow."
Defensive trio Fabio Aurelio, Martin Skrtel and Emiliano Insua will also miss the semi-final second leg at Anfield.