Liverpool manager Jurgen Klopp admitted he may be forced into the transfer market after the club's injury problems worsened during their League Cup semi-final first-leg win at Stoke.
Philippe Coutinho and Dejan Lovren went off with hamstring injuries and Kolo Toure ended the 1-0 victory with what appeared to be a similar problem.
Klopp had previously said he would not buy new players in January.
But after Tuesday's game he said: "This is something we have to think about."
Liverpool have no fit central defenders as Lovren joined Martin Skrtel and Mamadou Sakho on the sidelines, while Toure was clearly struggling at full-time.
Midfielder Lucas had filled in alongside the Ivorian at the Britannia Stadium after Lovren's first-half injury.
"Two weeks ago we had three centre-backs, which is a good situation, and the season started with five - but now it is zero," Klopp added.
"It is a strange feeling because on one side it is very, very good then we have these injuries."