A muscular issue caused Milner to miss the Boxing Day victory over Newcastle United, while Moreno was ruled out of that match due to a back problem.
And Jürgen Klopp confirmed on Friday that the Reds' vice-captain is not fit for the meeting with Unai Emery's side at Anfield, although he hopes to be able to call on him for Thursday's trip to Manchester City.
Dominic Solanke (muscle) is also out of the game versus the Gunners, but Moreno is in contention to play.
More to follow...