Rasmus Hojlund could not hide his surprise when Kobbie Mainoo was substituted against Burnley.
The young midfielder was replaced by Erik ten Hag in the 65th minute of the clash at Old Trafford with the score tied 0-0 at the time.
That decision was met with boos from the manchester united fans, who were unimpressed by the decision to replace the wonderkid.
Along with Mainoo, Hojlund was also substituted and both were replaced by Amad Diallo and Scott McTominay.
In footage captured by a fan in the stands, the Danish striker is seen walking across the pitch towards the bench when Mainoo's number was raided.
In response to the decision, Hojlund could be seen tilting his head with a bewildered expression on his face.
Ten Hag was questioned about the decision after the match and stood firm, saying: “I am the coach and I have to decide what the team needs.
“It was the right and totally logical decision to take out very young players who are in their first year in the Premier League and are feeling some fatigue.
“They (Mainoo and Hojlund) have had injuries this season and I want to protect them.”
Man United took the lead through Antony before Zeki Amdouni's late penalty. denied the Red Devils three points.
That result, plus Aston Villa's draw against Chelsea later on Saturday means Man United will not finish in the top four.
With fifth place unlikely to be awarded to the Premier League for an extra place in the Champions League, the 20-time English champions will have to settle for the Europa League or even the Conference League.