(CNN) Don't write off Manchester United or its manager Jose Mourinho just yet, says Wayne Rooney.

United has endured an uncertain start to the season, notably losing at Brighton with a performance that raised questions about the strategy of Mourinho and the inconsistency of the team's star player Paul Pogba.

"They have the quality, they just have to keep pushing," former Manchester United and England international Rooney told CNN Sport's Patrick Snell.

United plays Tottenham Hotspur on Monday at Old Trafford. If United loses it would trail leader Liverpool by six points.

Mourinho has welcomed three players to his squad over the summer -- Brazil midfielder Fred for $60 million, Portuguese defender Diogo Dalot ($24 million) and third-choice goalkeeper Lee Grant ($2 million) -- but the United manager has been unhappy that the club didn't sign a central defender.