
Osimhen scored an early penalty as Galatasaray beat an error-prone Liverpool, who lost goalkeeper Alisson and striker Hugo Ekitike to injury.
Liverpool made three changes to the line-up that suffered a first league defeat of the season by Crystal Palace at the weekend, with Mohamed Salah on the bench along with record signing Alexander Isak.
The win was a first in seven years at home in the Champions League for the Turkish side and a notable one against opponents who were unbeaten in all competitions until last weekend and now have dealt two losses in a row.
The second half brought a raft of substitutions but no change on the pitch, and Liverpool was still looking nervous in defence, with loose passing as Galatasaray worked constantly to keep up the pressure.