Wayne Rooney has one message for Angel di Maria's doubters: form is temporary, class is permanent.
United beat off strong competition from some of Europe's biggest clubs to sign Di Maria from Real Madrid last summer, but after a bright start, the £59.7milllion man has faded fast.
The low point of his United career came on Saturday when, after a poor first-half performance, he was substituted at half-time during the 2-0 win over Sunderland.
The Argentinian looked a pale imitation of the man who lit up the World Cup, made 17 assists for Real Madrid and was named man of the match in the Champions League final last year.
Rooney is convinced Di Maria will be a success at Old Trafford, though.
"It was one of those days that every footballer has," the United captain said when asked about Di Maria's performance.
"He's a great player. You don't lose your talent overnight. Hopefully he'll get back to his best and start giving some great performances.
"I think he will figure it out, we all have to. You have to come to it in your own way and I am sure he will be a big player for us."
Once referee Roger East had taken the controversial decision to dismiss Wes Brown instead of John O'Shea after awarding a penalty to United, it seemed only a matter of time before the hosts secured victory.
Rooney dispatched the spot-kick and added a second goal six minutes from time after Costel Pantilimon spilled Adnan Januzaj's shot into his path.
The goals were Rooney's first in the Premier League since Boxing Day, although his ability to find the net has been inhibited in recent weeks as he has been playing in midfield.
East came in for severe criticism for sending Brown off when it was clear O'Shea pulled Falcao back before the former England defender made contact with the striker.
Sunderland have decided to appeal against the red card and hope that Brown will be available for tomorrow's match at Hull.
"I think it was a penalty but I don't think it was Wes," said Rooney, who was stood a few yards away when Falcao hit the turf.
"It was tough but I would imagine it will get rescinded. In our view it was a clear penalty."
The Sunderland fans may have been unhappy with East, but it was the home supporters who were restless in the first half.
United's build-up play was often laboured and their final ball poor.
Some fans started yelling "Attack! Attack! Attack!" but Rooney thinks they must be patient.
"The fans are brilliant - they want us attacking at every opportunity but you can't do that all the time," he said. "Sometimes you have to work the opposition to tire them out which towards the end is how you win games."