Alex Ferguson has backed Japan playmaker Shinji Kagawa and Robin van Persie to carry Manchester United's attack while Wayne Rooney is out of action for the next four weeks. Rooney was stretchered off in the closing stages of United's 3-2 win over Fulham at Old Trafford and needed hospital treatment to stem the bleeding from a deep gash to his thigh suffered in a challenge with Hugo Rodallega. The injury, which rules Rooney out of England's World Cup qualifiers against Moldova and Ukraine, leaves Ferguson without his star striker for Premier League clashes against Wigan, Southampton and Liverpool, as well as the club's opening Champions League group-stage fixture. But the United manager is hopeful that Kagawa, a £17-million (HK$208-million) signing from Borussia Dortmund, and Van Persie, a £24-million capture from Arsenal, can prove more than adequate replacements for Rooney after marking their maiden appearances at Old Trafford with first-half goals against Fulham. Ferguson believes their partnership showed enough promising signs to hint at better things to come and he said: "It was fine. There will be a better understanding as time goes on but I was pleased with that. "We normally play with one behind, whether it's Wayne that plays in that role, Danny Welbeck can do it, Ashley Young and Ryan Giggs can play there. We've got options that way." Ferguson admits Rooney's absence will be a blow but the United star had started the day on the bench after being dropped following the 1-0 defeat at Everton. "It looked a really bad one and he's gone to hospital obviously and it looks as if he'll be out for four weeks," Ferguson said. Ferguson also showed concern with the way United allowed Fulham to score twice in sloppy fashion. Damien Duff got in too easily to score Fulham's first in the third minute and Nemanja Vidic's own goal after a flap by David de Gea gave the visitors hope following Van Persie, Kagawa and Rafael da Silva's first-half strikes for United. "You saw two sides of Manchester United in this match," Ferguson said. "It was cruise control but we made a terrible mistake for the second goal and it becomes a match when it should never have been." At least Van Persie got off to a flying start and the United star was relieved to have broken his duck for his new club. "It was a good goal, a difficult goal, but it was a good cross from Patrice Evra," he said. "The ball bounced just before it came to me, so I had to time it well and I did. It was a tight angle, but luckily it went in."