United are top of Group A although their qualification is not mathematically guaranteed so Mourinho will not be taking too many risks on Tuesday night.
Luke Shaw is certain to be in the squad, according to the United boss, who has yet to decide whether he will start the match or not, whilst Paul Pogba will play before a domestic suspension rules him out of this weekend’s derby with Manchester City.
“I am going to make a few, but not too many changes,” Mourinho said.
“We didn’t qualify yet, we didn’t finish first in the group yet, there are other clubs also involved in qualification and I need to keep a certain balance in the team.
“But when we speak about Luke Shaw, he’s working to have an opportunity and sooner or later that opportunity will arrive because he deserves that opportunity.”
Watford boss Javi Gracia does not think Abdoulaye Doucoure's form will be affected by his omission from France's latest squad.