Jonny Sutherland, Paddy McNair, Louis Rowley and Declan Dalley are the quartet in question. McNair made the most appearances last term, moving into a central defensive role with good effect, while Sutherland also kept goal for the Under-21s. Rowley and Dalley are both defenders.
"It’s only a technical point in terms of giving them more options if they can go out on loan or so on," explained coach Paul McGuinness to ManUtd.com, when asked about the third-year terms.
"It’s just a technical thing - we’re working hard so they have the same opportunity as everyone else to impress and push on."