DUBAI // The loss of Roger Federer, who as a four-time champion topped the bill at the star-studded Barclays Tennis Championships, is the latest in a series of major blows to hit this year's tournament. The gloss has been taken off the one of the most attractive women's events outside the grand slams by the Sharar Peer visa controversy and now next week's men's showpiece, already threatened by another potential visa problem involving the Israeli doubles player Andy Ram, might by deprived of the world's best two players. Before Federer announced his withdrawal late on Tuesday night, Rafael Nadal who last year deposed the Swiss at the top of the rankings, indicated he may also have to pull out of the 32-man tournament through injury. Both men suffered badly at the end of last season with their respective fitness problems. Federer's back pain is evidently more serious than Nadal's knee because he has declared an intention to take "a few weeks" off to give the damage time to heal. Nadal has given notice that the recurrence of the knee injury which kept him out of the end-of-season Masters Cup in Shanghai and Spain's Davis Cup final win over Argentina would not allow him to play in Dubai and in his country's ensuing Davis Cup tie against Serbia. His preference is likely to be the Davis Cup tie. Damaging though Nadal's absence would be to the US$2million (Dh7,346m) tournament, it is overshadowed by Federer not appearing in his adopted home for the first time since 2002. Colm McLoughlin, Managing Director of Dubai Duty Free, who organised this two-week tennis festival and were the original title sponsors, said: "Roger is a four-time winner here and a great fan of Dubai and the tournament. We are sorry that injury has prevented him from playing this year but we wish him a speedy recovery." "This decision was very difficult for me," said Federer, who will also miss Switzerland's Davis Cup tie away to the United States next month. "I won't just be missing one of my favourite tournaments of the tour, but also the chance to go through to the next round with my teammates." Federer, 27, who has not played since losing an epic five-set Australian Open final to Nadal last month, believes the problem which forced his withdrawal from the Paris Masters in October and impaired his challenge for the ensuing Masters Cup in Shanghai, has not been given enough time to heal. "After injuring my back last autumn, I did not have enough time to strengthen it completely," he said. " So I will use the next few weeks to make sure it is fully rehabilitated." Federer, so close to equalling Pete Sampras's record of 14 grand slam titles in Melbourne, is determined to be at his peak for the three other majors of the year, particularly Wimbledon where he has triumphed five times and the US Open which he won for the fifth time last year. His Dubai withdrawal and the considerable doubts about the participation of French Open and Wimbledon champion Nadal increases the prospects of Britain's Andy Murray completing a Middle East treble, the Scotsman having retained his Doha title last month a week after his splendid triumph in the inaugural Abu Dhabi exhibition tournament. Andy Roddick, the big serving American who capitalised on Federer's first round Dubai exit at the hands of Murray 12 months ago, will also be eyeing a repeat win, while Novak Djokovic, winner of the Masters Cup in Nadal's absence, is another contender whose chances have dramatically improved.