Max Johnstone, also a keeper, joined United's U18 team this season from Fleetwood.
Sam, now on-loan with Aston Villa, told manutd.com: "Max is enjoying it.
“I think, at first, it was an eye opener for him, coming to Manchester United, but he got his head down and he works hard with the Under-18s and the Reserves and the goalkeeping coaches.
“He's improving and we'll see what happens with him. Hopefully, he can stay and keep learning from the coaches and the players. He loves it.
"He lives in my old digs (lodgings) now... he lived with me at my place for a bit, until I kicked him out! But I always check up on him and make sure he's behaving himself!"