It means a chance for Ighalo to face his former club.
Solskjaer said, "Odion, it's special for him against Watford, he will be involved, he's in the squad, he's been training really well, he was the top scorer in round robin we just finished.
"He's not lost any of his quality, it's been difficult for him to be out of the squad as many times because he did really well up until the summer.
"This season he's not had as many opportunities and not let himself down as a professional and a human being. He's always a positive influence in the dressing room. Hopefully I don't need to put him on that we need goals, but hopefully he can join in."