United were beaten 2-0 by high-flying Everton at Goodison Park on Sunday, marking a nightmare return for manager David Moyes, who departed Merseyside at the end of last season.
The fallen Premier League champions are now officially out of contention to qualify for next season's UEFA Champions League, with the team languishing in seventh spot, 13 points adrift of fourth-placed Arsenal.
Former Liverpool defender Carragher blasted United following their 11th league defeat.
"That's the worst I've seen from them over 90 minutes," Carragher told Sky Sports post-game.
"When I played it was total dominance from Manchester United. I’m looking at this team and wondering why they didn't play like that when I was playing.
"Shinji Kagawa on the left wing must wonder what this English football is all about. Nobody seems to know what’s going on on the pitch or in the dug-out.
"You can't see what the plan is, what they're trying to do."
The Premier League giants can qualify for the Europa League, though they must overhaul Tottenham, who occupy sixth spot.
United, with one game in hand, have remaining fixtures against Norwich City, Sunderland, Hull City and Southampton.
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