De Gea: Manchester United must exert more control
United last won consecutive matches in September and the inconsistent start to the season has led to speculation over Jose Mourinho's future.
Fresh criticism of the manager's methods was prevalent after the Champions League loss to Juventus in which the hosts managed less than 40 per cent of possession.
De Gea, one of few positives in Tuesday's defeat at Old Trafford, believes the key to improvement rests with exerting more control.
"The team has produced some good performances, while others haven't been so good," the Spain international told Sky Sports.
"I think at times we've been relying on moments of brilliance from our attacking players.
"We haven't been 100 per cent solid defensively. We are improving, but I think we have to improve in all areas.
4 - Manchester United suffered their fourth home defeat in their last 13 games at Old Trafford in all competitions – as many as they had in their previous 81 home matches. Struggle. pic.twitter.com/AW1s0h8KKt
— OptaJoe (@OptaJoe) October 23, 2018
"It's true that it seems we need to concede for the team to react, attack and create chances. I don't know the reason why.
"We have to control games, create chances and improve from the start."
De Gea is out of contract at the end of the season, although United do have the option to extend his deal for a further year.
Mourinho recently revealed he was "not confident" but "not worried" about the prospect of the 27-year-old prolonging his stay.