The Red Devils have often used young players within first team training to make up the numbers.
The 16-year-old got a chance to impress new boss Ruben Amorim, as players come back in after international commitments.
Per Manchester Evening News, Thwaites has slightly gone under the radar at the club.
United had the following players involved in the session:
Academy players involved:
Jaydan Kamason, Jack Kingdon, Sam Murray, Finaley McAllister, Ruben Curley, Malachi Sharpe, Godwill Kukonki, Louis Jackson, Ethan Williams and Jim Thwaites.
Senior players involved:
Tom Heaton, Leny Yoro, Tyrell Malacia, Mason Mount, Kobbie Mainoo, Casemiro, Amad, Antony, Marcus Rashford.
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