Mourinho feels Man United came to their third consecutive loss of the season as a result of the negativity among the players.
The club had made a strong start to the season under the Portuguese boss, but have dropped six points in their last two league games.
Speaking after the defeat, Mourinho claimed Young brought confidence to the game.
“I feel the first moment we had a defeat, a difficult situation, some of the boys are having a bit of difficulty coping with the negativity,” he said.
“You see Ashley Young, his mentality the happiness and confidence he brought to the game is something more players need to have.”
United’s loss streak started with a 2-1 defeat to rivals Manchester City which seems to have unnerved the dressing room.
Jose Mourinho‘s side came out against a confident Watford side following their 4-2 victory over West Ham and they struggled to keep up with the home side.
His comments don’t really match up with what happened on the pitch which is why it’s odd, shortly after Young was introduced, the Englishman had the chance to shoot at an open goal, but instead opted to pass the ball down the wing.
Young’s performance showed he had confidence issues, but as Mourinho suggests, he brought the right mentality in to game and showed urgency to try and win.