The midfielder went down off the ball just 19 minutes and immediately appeared to be in distress, seeming to indicate a problem with his back.
After receiving treatment on the pitch, Keita was eased on to a stretcher and then driven off on the back of a buggy, with Jordan Henderson taking the 23-year-old's place.
A blow for Liverpool early on as Naby Keita goes down off the ball and is stretchered from the field— Omnisport (@OmnisportNews) October 3, 2018
Jordan Henderson comes on #LFC #NAPLIV #UCL
Live blog https://t.co/SHARvZYvMV pic.twitter.com/WA8jkwH55y
It is a disappointing blow for Keita, who is yet to make much of an impact following his big move from RB Leipzig.