American Mardy Fish announced Wednesday that he has withdrawn from the US Open because of a health problem. Fish, who was once ranked as high as seventh in the world, has been fighting to make a comeback after heart issues over the past two seasons, but will now have missed all four Grand Slam events this year. \"Friends, unfortunately my health won\'t allow me to compete this year at the US Open. Thank you for all your support,\" Fish posted on his Twitter page. Fish retired in the third set of his second-round match against Jarkko Nieminen on Tuesday at the ATP Winston-Salem Open due to heat stroke. Fish, 31, is 3-5 in ATP matches this season, two of the triumphs coming in a third-round run at Washington last month. He lost his first matches at Cincinnati and Winston-Salem and has slid to 173rd in the world rankings. source: AFP