The 18-year-old impressed in his first senior start for the club against Everton in the Premier League on Sunday and manager Erik ten Hag said he would have no hesitation throwing him in again in what is expected to be a hostile atmosphere in Istanbul.
"No, we don't have fear [of starting Mainoo]," Ten Hag said. "If players are good enough, then they are old enough."
The Dutchman added: "We are very pleased with the performance, but it is one performance. You have to do it on a consistent basis.
"Kobbie is so mature, he knows that. We are confident he will do it, but first you have to prove it, as we all have to prove. You are only as good as your last game."
United are struggling with a lengthy injury list as they look for the result needed to revive their fading hopes of reaching the knockout stage from Group A.
The likes of Casemiro, Christian Eriksen, Jonny Evans and Mason Mount are all injured, while Jadon Sancho continues to be banished from the squad and Donny van de Beek is not registered for the Champions League.
Marcus Rashford is serving a one-match ban after being sent off in the 4-3 loss at FC Copenhagen earlier in November, but both Rasmus Hojlund and Antony are fit again and start in attack after missing the win at Everton.
Unavailable: Jadon Sancho
Suspended: Marcus Rashford
Time and date: 5:45pm GMT on Wednesday November 29, 2023
Venue: Rams Park