"Liverpool have lacked an out-and-out goalscorer, someone who can get them 20 to 25 goals a season and Fernando Torres will give them that," said Rooney. "He can provide that extra push to try and win the league for them.
"And Wenger is also building a new side. Thierry Henry going is obviously a big loss. But they have still got a big chance. Eduardo Da Silva will be good for them.
"I've faced him for Croatia and he is a top player. Spurs can also start to push the top four with the signings they have made."
But for all the challengers to United's crown, Rooney is convinced Fergie's men can stay ahead of the pack.
"We have a big squad now and it's probably the best squad of players I've ever played with," said Rooney. "Hopefully we can challenge for all of those trophies because that's what this club is all about.
"Winning the title definitely makes you more determined to hold on to it. It makes you want to work that much harder to achieve it."