Ole Gunnar Solskjaer claimed the officials were wrong to award Crystal Palace a penalty but said it was not the reason why Manchester United lost.
Palace were awarded a second half spot kick when the ball struck the arm of Victor Lindelof.
Ole Gunnar Solskjaer said his side lacked match fitness
David De Gea initially saved Jordan Ayews strike but they were made to retake after the goalkeeper had jumped off his line. Wilfried Zaha made no mistake at the second attempt.
It was a disappointing performance from Man United as they lost 3-1 and Solskjaer put that down to a lack of match fitness.
He told talkSPORT: Thats not what lost us the game. We didnt do enough to win the game from start to finish. That was the main point for me. We are way off sharpness, fitness wise.
They came out of the traps quicker than us, better than us. Better on the ball than us. Off the ball better than us.
“The penalty decision I thought was wrong. Great save by David but if you follow the rules it was probably the right decision because he was one inch off the line. It was harsh but if you follow the rules it was probably the right one.
Crystal Palace were awarded a penalty when the ball struck Lindelof’s hand
We were second best. Who knows what could have happened if there was no penalty. The conclusion is, not good enough and we need to improve quickly.
We have to train hard and get the players match fit and get them gelling again. Get the mojo back again. We were fantastic one month ago in Europe and after the restart. We have to find that back quickly.
When asked if the short break had an effect, Solskjaer said: Definitely. They were sharper than us, quicker than us. They were more prepared physically.
“I believed they had four friendlies and this was their third competitive game. We just started the league today and some of them will definitely improve.
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“This is not them at their best but we did go far in Europe and it might harm us for a little while but well get back to it.
Man United fans will also be desperate for news of any incoming transfers but Solskjaer did not give anything away.
When asked about any possible incomings, he said: You can see on the pitch we can play so much better than we did. Thats the thing. Its going to be a long season. We are going to catch up fitness wise but the main thing is that we improve with the ones that are here and well see what happens.