United recorded an unambitious goalless draw in the away first leg against Sevilla to give themselves the slightest advantage heading into last night's second leg at Old Trafford, but they subsequently slumped to a 2-1 defeat to end their involvement in this season's competition.
The Red Devils produced only four shots on target throughout the two legs, and Scholes believes that the attitude of the players must be called into question following such a tepid display.
"It's difficult to describe how bad that was. Lethargic, bad attitude... [Mourinho] said in his interview he was happy with their attitude, but he has to be protecting his players," he told BT Sport.
"The players have let him down tonight by being so mediocre against a poor team. You are going for a place in the Champions League quarter-final and there was no desire, heavy legs.
"It was poor. You can accept an off night if the attitude is right, but it wasn't."
United have now reached the quarter-finals of the Champions League just once in the past seven seasons.