Ighalo has made two substitute appearances since he joined the Red Devils on a six-month loan.
The Nigerian striker was introduced late on against Chelsea in the Premier League and Club Brugge in the Europa League.
Greenwood was not in the team that faced Club Brugge on Thursday due to illness, but Martial has started nine of the last 10 matches.
“Everyone says that (players raise their game) against their old team when they score, but there are also many games when you don’t score.
“Odion is getting more and more minutes, but (whether he starts) depends on Mason as well of course, and how Anthony (Martial) is (after playing on Thursday),” Solskjaer told MUTV.
Ighalo spent two and a half years at Watford, before leaving to Changchun Yatai in January 2017.
Affairsofnaija Reports (AON)