Lionel Messi grabbed a brace and Philippe Coutinho curled one in from
And Fletcher believes that games such as that are revealing of each player's character and feels the knowledge of which squad members are mentally prepared to face adversity will help Solskjaer as he looks to overhaul the squad at the end of the season.
“Last night when you’re 3-0 down, that’s when you’re looking at the character of your players," Fletcher said on talkSPORT.
"Who’s still playing? Who has not given in?
“He’ll have learned probably more from that than he has from winning games.
“The challenge is down to the players now.
“Ole Gunnar Solskjaer is the manager, so from now until the end of the season your performances have got to reflect if you want to be part of Manchester United’s future.
“If you don’t, thanks very much. The club is too big, we’ll move on, we’ll get new players.
“That’s the challenge ahead for these players now.
“Everyone has got to step up now. I think it’s a test of who wants to be there."
The Red Devils must dust themselves down and go again, with a fierce top-four battle to see to in the Premier League. Failure would result in the absence of Champions League football at Old Trafford next season, something the club can ill-afford when trying to lure top players.
Solskjaer's men have lost five of their last seven games in all competitions, however, and their poor form comes at a bad time, with fixtures against Everton, Manchester City and Chelsea still to come.
Their final two games of the season look easy enough on paper, visiting relegated Huddersfield and hosting struggling Cardiff, but if they fail to take enough points from their next three games it could be too little, too late.