Liverpool's Swedish national team striker came on in the 67th minute with the match in the balance.
From the bench, Isak watched Liverpool take the lead in the sixth minute after Ryan Gravenberch scored to make it 1-0. Chelsea responded almost 30 minutes later through Enzo Fernández.
It proved to be the last goal of the match, although Cole Palmer thought he had made it 2-1 for the away team early in the second half. However, the VAR room ruled the goal offside.
The result meant that Chelsea broke their six-game losing streak in the league.
