The Reds' No.9 was forced off shortly before half-time of Saturday's Premier League clash at Anfield.
Post-match, Jürgen Klopp said: "Serious? I don't know. Serious enough to take him off, yes.
"Bobby felt his hamstring, came and told us so we had to prepare the change. Bobby is nobody who raises the hand when he doesn't feel anything.
"It doesn't look too serious but you never know before you have a scan, which will happen tomorrow."