Stan Wawrinka's tuneup for the US Open will have to wait at least two weeks, as the world No. 4 announced Wednesday he is pulling out of the Rogers Cup and the Western & Southern Open with a knee injury.
Wawrinka has not won a match since reaching the French Open final in early June. The three-match skid includes a stunning opening-round loss against Daniil Medvedev at Wimbledon.
"After much backwards and forwards and consultations with my doctors and my team, unfortunately I have decided to skip Canada and Cincinnati to be on the safe side, even though I've been battling hard to make these events," Wawrinka said in a statement released through his management company.
"Hugely disappointing for my fans and myself that I have to make this decision, but I need to be 100 percent confident before I resume competition till the injury that plagued me in Wimbledon has been resolved. My team and I are doing everything possible to make this a speedy recovery."
Wawrinka has historically thrived during the summer swing, most notably at the US Open, where was won the title a year ago. Wawrinka has not fallen before the quarterfinals of New York in the past four seasons.
"Stan has always been loyal to our tournament and we're obviously disappointed he won't be here this year," Rogers Cup director Eugène Lapierre said in a statement. "Stan is one of the best players in the world and we wish him a quick recovery and best of luck for the rest of the season."
The Rogers Cup will begin Aug. 7, followed by the Western & Southern Open in Cincinnati on Aug. 13.