Erik ten Hag has sent a message to Alejandro Garnacho after the substitute was substituted in Manchester United's win over Crystal Palace.
The Red Devils returned to the Premier League win column as they beat Palace 2-1 on Saturday in a game which saw Casemiro red carded for grabbing Will Hughes around the neck.
Bruno Fernandes opened the scoring from the spot, with Marcus Rashford continuing his fine form in front of goal with an easy finish to complete a brilliant team move.
As mentioned, Casemiro was shown a straight red card for his actions towards Hughes during a melee between both sets of teams.
Jeffrey Schlupp then pulled one back, with Ten Hag making a change to sure things up for the closing stages of the match.
Garnacho, who entered the fray as a second-half substitute when he replaced Wout Weghorst, was taken off for Harry Maguire in the 87th minute.
The 18-year-old cut a frustrated figure on the bench when his latest Man United appearance lasted just 38 minutes.
Ten Hag recognises it's 'not always nice' to bring off a player who had just come on, but insists it was in the 'interest of the team'.
"First we had to see how they changed, then you have to anticipate and see how we can close, how to be compact, how we close the gaps, how we get away from our goal but also still have a threat in attack," he explained.
"I think we had to change something. It’s not always nice bringing off a player who we brought on but it’s in the interests of the team and the player has to accept that."
The Argentinean youth star has featured in 10 league game this season and has scored one goal - a match-winner against Fulham back in November.
Across all competitions this season, he's played 21 games, scoring two goals as he's getting regular minutes under his belt.