United finished second last season – 19 points behind the champions Manchester City in what was a history-making season for Pep Guardiola’s side when they hit the 100 point mark.
Nev and Carra’s top-six verdict
Sky Sports reports United are preparing a bid for Leicester’s Harry Maguire before the Premier League transfer window closes on Thursday.
Rooney, who now plays for MLS’ DC United, has admitted his former club may need to add one or two players in order to win the title this season.
United’s record goalscorer said: “I think it will be difficult after the season they had last year. They [Manchester City] have been playing some great football.
“But I hope someone can catch them – it would be nice, so hopefully Manchester United can. I think maybe another signing or two.
“I am sure Jose (Mourinho) has been getting the team right. I know there has been a lot of talk about pre-season in the press but I am sure behind the scenes, Jose has been giving them the right amount of work.
“They have the game against Leicester on Friday so hopefully they can go one step further this year than second and try and get the title back.”
Mourinho’s side take on Leicester on Friday in the Premier League season opener.