David de Gea has conceded there is a "lack of quality" within the Manchester United squad.
United sit ninth in the Premier League table following last weekend's draw with Sheffield United.
They return to action against Aston Villa on Sunday, nine points adrift of the top four.
Speculation over Ole Gunnar Solskjaer's future has stepped up in recent weeks following Tottenham's dismissal of former managerial target Mauricio Pochettino.
De Gea insists United's players are working hard to arrest their slide but concedes some of the squad are simply not up to it.
"The team is what it is, and results are what they have been recently," De Gea told Sky Sports.
"We need to win four or five games in a row to be at the top, but at the moment the team is not playing so well.
"We're giving it everything, we're trying to get those big wins that can put us high up in the table, but the truth is at the moment we're not consistent enough, there's much to train and much to improve.
"I don't think it's through any lack of effort, the boys are leaving everything out on the field in training and games. You could point maybe to a lack of quality in certain areas, but certainly not a lack of fight."
De Gea signed a new deal in September and admits he feels settled in Manchester, playing down talk of a return to Spain.
"We've been here for a lot of years and I feel like people appreciate me here, I've made a lot of friends and I'm thrilled to be part of this club," he added.
"It's been a long time that I've been playing here and it's not an easy thing to keep playing at the highest level and to maintain that level.
"I personally hope that we can get more accolades in years to come by working hard and playing to that same high level."
