Manchester United great Roy Keane questioned whether his former club is perhaps "too big" for manager Jose Mourinho.
Despite reaching the Europa League quarter-finals with a 1-0 win over Rostov on Thursday, Mourinho moaned about United's busy run of fixtures.
Keane, a former captain and seven-time Premier League winner at United, was furious with Mourinho, saying the Portuguese tactician needed to embrace the demands of managing at Old Trafford.
"I've never heard so much rubbish in my life. Why do we have to listen to that garbage? It's just utter nonsense what he's talking about," the Irishman told ITV.
"He's manager of Manchester United, one of the biggest clubs on the planet, the squad he's got, the players and he keeps moaning about fixtures and fatigue.
"We were just looking at some of the cup draws they've had. They've had an easy way in the cups, some good draws, a lot of home draws, and the guy is talking absolute nonsense.
"I've never heard so much rubbish in my life. Maybe the club is too big for him, he can't deal with all these demands at the match. What matches? Man United reserves could've won that game."
United were beaten at Chelsea in the FA Cup on Monday before overcoming Rostov, with a clash against Middlesbrough in the league awaiting them on Sunday.
Making matters worse for Mourinho, Paul Pogba and Daley Blind suffered injuries in the win over Rostov.