Young has been out injured for several months but stepped up his recovery with a 59-minute cameo in United’s Under-23s draw against Swansea on Monday night.
The 32-year-old struggled for consistent game-time under Mourinho last season and has been linked with leaving Old Trafford this summer.
But the versatile winger is eager to prove he can play a key role for United this term, saying: “It’s great to be back.
“As a player, you want to be back on the pitch and it was good to get minutes under my belt.
“I’m feeling good, I’m feeling fit. I could’ve played longer, but I was brought off.
“Whenever the manager calls on me, I’m ready to go”
Man Utd star Ashley Young
“I’ve worked hard since I had the operation done 13 weeks ago so I’m happy to be back out there.
“I’ve been training with the team for 10 days or so now.
“So, whenever the manager calls on me, I’m ready to go.”
It is unlikely that Young will be able to make United’s squad for their clash against Leicester this Saturday.
But he could feature after the upcoming international break when the Red Devils make the trip to Stoke on September 9.