Roy Keane criticised Manchester United's desire after their goalless draw at Arsenal saw them lose ground to Premier League leaders Manchester City.
Edinson Cavani missed a golden opportunity to slot in the winner in the second half but former United captain Keane said Ole Gunnar Solskjaer's side looked like they lacked the belief to see off an Arsenal side missing key men Bukayo Saka, Pierre-Emerick Aubameyang and Kieran Tierney.
The result, coming on the back of United's midweek shock defeat at home to bottom-club Sheffield United, coupled with City's Saturday win over the Blades, leaves United three points behind their neighbours, who have a game in hand.
"I'm scratching my head with United. The worry for me watching them today, they almost lacked the belief they could go and win the game," Keane told Sky Sports.
"It's Man Utd, you're looking at Arsenal who are missing a few players, the game was there for the taking.
"Overall their performance lacked that intensity. There was a real lack of quality today from Man Utd, and a real lack of conviction and desire to go and take the game to Arsenal. And Arsenal certainly deserved their draw, at least."
United were unlikely table toppers earlier this month after recovering from a slow start to the season and benefitting from teams above them slipping up.
However, Keane says he is concerned by how they have reacted to being considered as title contenders.
"Where they were the last few months, they were getting the plaudits and they were just kind of sneaking up the table. But they got in the habit of winning football matches, even if they weren't playing great," he said.
"But all of a sudden, the last three or four weeks, when they've got to the top, people are saying 'can you win the league, can you compete with Man City?'. And it looks as if the players have got almost frightened of the challenge, 'I don't think we're ready for that yet'.
"That Sheffield United result can happen. And if you turn up with a bad attitude it is going to happen.
"But today I'm scratching my head at this team. You play for Man Utd, and Ole keeps talking about these players, saying 'they're winners, they're winners'. Well come on, then. Show us. It is Man Utd. You signed to win football matches, to win big prizes.
"My worry, having watched them today - and I've had question marks over this group of players for the last number of years - I look at them, you've got into this great position, are you ready for it? And it looks like they're almost frightened of it. You're playing for Man Utd. Grab it. Go for it.
"They didn't do it today."
While Solskjaer attempted to take the positives from the performance and result after the match, Keane believes United will look back on the past week with regret come the end of the season.
"This Arsenal team are eighth in the league and they were missing three of their best players," he said.
"Man Utd and Ole afterwards are going, 'ah, we take the draw'. Too many draws when a team is there for the taking doesn't win you the big prizes.
"At the end of the season, when you look back, those four or five points we lost in those three or four days: huge.
"It really takes its toll at the end of the season when you reflect. At the moment you might try to pretend it's not that important but it is vitally important - especially when they're there for the taking."
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Carra: United missing fantastic opportunity
Sky Sports pundit Jamie Carragher believes, given the circumstances of this unusual season and the injury problems at pre-season title favourites Manchester City and Liverpool, United have a "fantastic opportunity" to compete for the championship.
However, he says, despite what are positive results on paper - drawing away at Liverpool and Arsenal - United are not showing the attitude needed to win the Premier League.
He also warned that waiting for the team to develop and 'be ready' for a title push next season is a dangerous tactic, with City and Liverpool potentially even stronger in 2021/22.
"I had this debate with Gary Neville on the back of [the 0-0 draw at Anfield] and it's the same tonight," said Carragher. "Normally going to Anfield or away to Arsenal and getting a point is not a bad result.
"But I'd be more angry as a United fan today than I would be in midweek. Yes, it's a game you should win, Sheffield United. But these things happen at times and you lose a game you shouldn't.
"But it's almost like United can't believe where they are. People keep saying United aren't ready to win the league, or they're not good enough.
"But there's this idea they're building and next year could be the year they go for it.
"Man City this season have no strikers, Liverpool have got no centre-backs. It is a strange season and maybe someone will qualify for the Champions League that we don't expect.
"For Man Utd, this is a fantastic opportunity in the situation they find themselves in right now - but it's almost like they're happy to be there.
"The results are not bad, in terms of today and Anfield, but I don't see the intensity or the energy of 'we're fighting for the league, we've got to go for this'.
"They should have won those two games.
"This idea that next year will be Man Utd's year... Liverpool and Man City might go back to 95, 96, 100 points next season.
"I think it's a big opportunity and they'll be kicking themselves on the back of these two performances."