Ighalo made a superb start for United, scoring five in his first four starts before the lockdown, yet the Nigerian has seldom impressed since European football restarted in June.
Cavani has not travelled to France for the Champions League group stage opener against former club Paris Saint-Germain and Ighalo - back on the bench for United at Newcastle - is expected to be named as a substitute tonight.
Solskjaer said, “I think as a team and a club we always want to get players in. And I think Edinson coming in, we'll give him time to adapt to the Premier League and get his sharpness and fitness back.
“We've had some very good performances by Odion and he's still a very important part of this squad."