Manchester United manager Sir Alex Ferguson has backed Chelsea to challenge for the Premier League title this season.With both Manchester United and rivals Manchester City having got off to the perfect start to the campaign with each securing four wins from four, some have already moved to write off the division as a two-horse race for the title but the Scot insists that Andre Villas-Boas' men will be pushing for the crown."The games with Chelsea over the last seven years have been very close affairs. There's usually only one goal in it and I think it will be very tight again on Sunday," Ferguson said ahead of the two sides' clash at Old Trafford."They are a team of great experience and all the publicity has been going to Manchester so Chelsea have been in the background and they will have been enjoying that.""Chelsea will be there at the end of the season. There's no doubt about that."Ferguson also confirmed that his side came through their 1-1 draw away to Benfica in the Champions League on Wednesday largely unscathed and admitted he is facing a number of selection dilemmas."We came through the Benfica game without any injuries," Ferguson said. "We have a strong squad for Sunday. It will be a fantastic game.""They're all giving me headaches - Darren Fletcher, Ji-Sung Park, Antonio Valencia. They've not been involved because the team have been playing so well. I've decided not to tinker with that, but now we come to the time of the season where we need our squad - we've got European games, Carling Cup etc."The United chief has also been bolstered by the quick return to fitness of Danny Welbeck who, despite being unavailable for Sunday's fixture, could be back playing away to Stoke in a week after injuring his hamstring in the 8-2 demolition of Arsenal.