In a crunch match that could go some way to deciding who will make the Champions League next season, tempers were already running high.
At the end of the first half, Keita caught Frankfurt's Makoto Hasebe with a late challenge. The Japanese midfielder took exception and pushed Keita, resulting in all 22 players getting involved in a brawl.
The timing was fortunate as the referee managed to calm the situation and get everyone into their dressing rooms for half time and by the time it had finished, the situation had largely diffused.
Keita was forced to leave the match after an hour with a thigh problem. Liverpool have agreed to sign the Guinea international for around €60million.