Mourinho intends to play a weakened side against Palace in a bid to keep his senior stars fit and fresh ahead of the Europa League final.
Mourinho intends to play a weakened side against Palace in a bid to keep his senior stars fit and fresh ahead of the Europa League final against Ajax in Stockholm next Wednesday.
With United unable to finish in the Premier League's top four, Mourinho is banking on winning the Europa League to seal a place in next season's Champions League.
That means Joel Pereira, Kieran O'Hara, Demetri Mitchell, Scott McTominay, Josh Harrop, Matthew Willock, Zachary Dearnley and 16-year-old midfielder Angel Gomes will all be involved at Old Trafford this weekend.
Asked if the young players were ready, the United manager said: "All together? No.
"I think one in the middle of a good structure, a dynamic structure, an experienced structure, I think, yes. I think lots of them together, no."
Mourinho confirmed 19-year-old defenders Tim Fosu-Mensah, back after a shoulder injury, and Axel Tuanzebe would also play on Sunday.
"The only positive is to save my players to give them better conditions for Wednesday," Mourinho said.
"Of course individually for the kids, I think it will be a great experience: Old Trafford, Premier League, Crystal Palace, last match of the season.
"I think for the kids it will be a big occasion, it will always be good experience for them.
"But I think the best debut for a young player is in the middle of an experienced structure, where he can be supported.
"To play so many kids at the same time, honestly, I don't think it's good.
"Obviously there is a big difference of quality, strength, experience between them and good players, experienced players like Crystal Palace have.
"I would prefer to give them debuts like I gave to Axel against Reading, to Joel against Wigan - or a big match, but for one player."
It will not just be kids playing against Palace as Mourinho confirmed £89 million signing Paul Pogba will start after missing the past two matches following the death of his father last Friday.
"Paul is fine," the United manager said. "Strong guy, strong mentality.
"He is learning how to live after his father passed away, but he is strong, and he knows he needs to play next Sunday because he hasn't played or trained for a long time and he needs these minutes on the pitch. He plays against Palace."
Marouane Fellaini is having a hamstring injury assessed, while Chris Smalling is set to be fit for Wednesday's final despite a "small problem" keeping him out against Palace.
Zlatan Ibrahimovic, Marcos Rojo, Luke Shaw and Ashley Young are definitely out of the Europa League final, with Mourinho bemoaning United's injury situation when previewing the Ajax clash.
The Portuguese also spoke of the "unbelievable" fixture schedule and took aim at those that "like to lie" about United's situation.