The Red Devils have five points after four matches, putting them seven behind their bitter rivals Liverpool.
But Mata thinks the performances have been there and United have not gotten the rub of the green.
"We started the season really well against Chelsea at home, winning 4-0 (with a) great second half, I would say and after that, at Wolves we felt we dropped two points," he told MUTV after a 1-1 draw with Southampton.
"We lost against Crystal Palace at home which we shouldn't accept and it shouldn't happen again, and today another two points dropped.
"We need to find this consistency and try to win and add three points after three points and that's our main objective.
"I think we are deserving more in almost every game but deserving is not enough: you have to get it."