The midfielder went down off the ball with a back problem, and after being attended to, he was hauled off on a stretcher.
Keita was replaced by Jordan Henderson in a game lost by the visitors after Lorenzo Insigne's late strike gave Carlo Ancelotti's men the victory.
And, ahead of weekend's top-of-the-table Premier League fixture against Manchester City, the German handler said he is unsure of the availability of the summer recruit.
“It is back, that's what I heard. I don't know exactly. We have to wait," Klopp said.
Also, the club confirmed that the Guinea international was taken to a hospital in Naples during the game.
"Keita was transferred to a local hospital with the club doctor, where - with the midfielder’s agreement - he underwent a number of precautionary health checks to assess his condition," read a statement on club website.
"No decision has yet been taken on when the 23-year-old will be discharged.
Since his arrival from RB Leipzig, the 23-year-old has played nine times and might have to wait longer for his 10th outing.