World number three Stefanos Tsitsipas retired injured from his second-round match against Australian Alexei Popyrin with what appeared to be a right arm problem on a bad day for seeds at the Paris Masters on Wednesday. The 23-year-old Greek was trailing 4-2 during the first set when he called the trainer on court before shaking hands with his opponent to signal his retirement. Tsitsipas declined to share details of his physical condition but added that he did not want to aggravate the problem