A graphic on Match of the Day over the weekend showed that the Red Devils had been outrun in all but one of their Premier League matches so far this term.
United sit 12th in the league table after their dramatic 1-1 draw with Tottenham, where Dominic Solanke salvaged a point late on for the visitors, who had been reduced to ten men after Rodrigo Bentancur’s red card for headbutting Luke Shaw.
Bryan Mbuemo had put the hosts ahead at Old Trafford against the run of play, with Spurs dominating proceedings for much of the encounter.
Now, Rooney, the former United striker, believes that his old employers’ lack of aggression is harming them.
"I think in a lot of games, they've been happy to go into a mid-block,” he explained.
"If you think back to Jose Mourinho and his first Chelsea team, they were a mid-block team, but when the ball got moved side to side, they were aggressive.
"That meant getting up in your face and they were horrible to play against.
"Right now, United are in a mid-block, but they're not getting up to the ball. That means they're not a difficult side to play against.
"The players are running, but they don't have that aggression to get up to the ball, so they're stuck and that needs to change."
Carrick’s men travel to Atletico Madrid in the Champions League on Tuesday, before an away game against fierce rivals Leeds United on their return to Premier League action.