McNair has made just nine appearances for Louis van Gaal’s side this season, having struggled to hold down a regular starting spot.
The 20-year-old started Monday’s fixture as a centre-back, and Joyce, United’s under 21 coach, admits he wasn’t surprised to see the youngster on the score-sheet.
"He's done it before. He's a good footballer. He came to the club as a No.10,” he told MUTV.
“We know that he's got good feet. We know that he's got good technical ability.
“He went through a massive growth spurt when he was under 18 and came out of it and ended up playing in more backward positions, but he's done that before for us.
"Against Reading, a couple of years ago, he got the goal to get us in the play-off finals with a last-ditch winner. There's a good finisher in there and he's come up trumps again."
Wayne Rooney also made his return from injury against Middlesbrough, playing 60 minutes.
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