(CNN) -- Juan Martin Del Potro has confirmed that he will not defend his U.S. Open title in New York, following women's No. 1 Serena Williams in withdrawing from the final tennis Grand Slam of the season.
The Argentine has been sidelined since January, when he lost in the last 16 of the Australian Open, and needed wrist surgery in May.
The 21-year-old won his first Grand Slam title when he beat Roger Federer in an epic five-set final last September, but on Saturday ended any lingering hopes that he would be in the field when the New York tournament begins on August 30.
"I feel extremely sad to announce that I will not to be able to defend my US Open title," the towering 6ft 6in player said in a statement on the U.S. Tennis Association website.
"Winning in New York last year has been my major accomplishment in tennis and my best memory so far. I am so sorry for my fans, my sponsors and all the people that care about me, but I have only started practicing in the last two weeks and unfortunately I cannot compete at the top level yet.
Tournament director Jim Curley added: "We wish him all the best and look forward to his return next year."
Del Potro has fallen to ninth in the world rankings due to his absence from the ATP World Tour circuit, having won seven titles in the previous two seasons.
American Williams withdrew on Friday due to the foot injury she suffered after stepping on broken glass in a restaurant in July the week after winning her 13th Grand Slam singles title at Wimbledon.
She joined former No. 1 Justine Henin in pulling out, and the two-time U.S. Open winner's fellow Belgian Kim Clijsters is in some doubt ahead of her title defense after suffering a hip injury in Toronto on Friday.