Former Manchester United winger Nani has accused the squad of lacking fighting spirit and failing to follow the example set by captain Bruno Fernandes.
The 36-year-old won 12 trophies during seven years at Old Trafford which ended with a season-long loan move back to Sporting CP prior to joining Fenerbahce in 2015.
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Nani is at Turkish Super Lig club Adana Demirspor but addressed his old team's existing crisis, which worsened on Wednesday as United's defence of the EFL Cup ended with a 3-0 thrashing at home by Newcastle United.
Erik ten Hag is under mounting pressure after the club made their worst start to a season since 1962 and Nani told Portuguese podcast '1 PARA 1': "When we used to play at Manchester [United], one of the things that defined the club was that you could be losing 3-0 with 15 minutes, 10 minutes left in a game, and that's when you saw what mental strength means.
"It's no longer about talent, it's about pushing the ball into the goal. We did that, we did what was necessary.
"Now, when you watch Manchester play, you see a lot of talent, maybe more talent than in our time in terms of technique, and they're all technically gifted. But when you watch the game, there's no spirit of sacrifice, no fighting spirit... A real player, a star, at Manchester, has to unlock the game; if they don't, it won't work."
Fernandes has attracted criticism from other former United players including Gary Neville and Roy Keane, the latter suggesting he should be stripped of the captaincy after another petulant display in last weekend's derby defeat to Manchester City.
But Nani said of his fellow countryman: "Manchester already has great players. We have Bruno Fernandes. If Bruno Fernandes wasn't playing well, I'd criticise him too, but for example, the sacrifice and effort he puts into the game, he does it. We see it. He works hard, gives his all, and contributes. It's just that many others don't keep up with it."