Manchester United manager Ole Gunnar Solskjaer said he will carefully manage Cristiano Ronaldo's playing time but has to balance that with getting the 36-year-old Portugal forward settled into the side.
Ronaldo, who has rejoined United after 12 years away, marked his comeback at Old Trafford with two goals in Saturday's 4-1 Premier League win over Newcastle United.
United return to action in Tuesday's opening Champions League group stage match against Swiss club Young Boys and Solskjaer said he would not rule out resting Ronaldo.
"It's not impossible to leave him out," Solskjaer said. "He is 36. Mason (Greenwood) is 19 so it's the same, I have to manage his minutes and I have to manage a 36-year-old's minutes as well.
"The other thing with Cristiano is that he looks after himself so much so I know he will recover quickly and he has had a pre-season.
"Of course, it's important that we get everyone up and running and to get him up and running and to give him 90 minutes."
United are joint top of the Premier League on 10 points after four matches. They travel to West Ham United on Sunday for their next league match.
