Garnacho, who is on loan at Chelsea, was left on the bench by manager Enzo Maresca for the 2-1 defeat at Old Trafford.
Throughout the game, he was jeered by the home crowd, who accused him of lacking loyalty after leaving the club.
However, some senior United players felt the fans were too harsh on Garnacho, and they expressed sympathy for him.
A source close to the team stated that Garnacho is a talented player, but he had been difficult to work with during his time at Manchester United.
According to the source, some players tried to talk to Garnacho about his behavior, but he didn't always listen.
The source also mentioned that many players felt sorry for Garnacho, who received a rough welcome back at Old Trafford.
They believe Garnacho was poorly advised by those around him, which led to the negative reaction from the fans.
While some players have left Manchester United in difficult circumstances, Garnacho received an especially rough reception.