The Japanese international has struggled to force his way into Moyes's plans on a regular basis this season, having made 20 appearances.
However, with club-record signing Juan Mata cup-tied, Moyes has insisted that Kagawa will "definitely be involved" against the Greeks, who lead the two-legged tie 2-0 from the first meeting on the outskirts of Athens.
"Shinji's an important player for us. It's been a difficult time for him. he's not played as often as he'd have liked. He's someone we really like and he'll definitely be involved at some point tomorrow," Moyes told reporters.
Kagawa is yet to find the net for United in any of his outings this term.