Wimbledon champion Roger Federer withdrew Monday from the Western & Southern Open because of a back injury. He has won the Masters series tournament seven times.
The move was announced on the first full day of matches. This U.S. Open warmup has now lost five of the top six players in the men's rankings.
Federer, a 19-time major champion, said in a statement he "tweaked" his back last week at the Rogers Cup in Montreal, where he lost Sunday's final to Alexander Zverev.
The Swiss star, ranked No. 3, is sidelined along with No. 1 Andy Murray, No. 4 Stan Wawrinka, No. 5 Novak Djokovic and No. 6 Marin Cilic, the defending champion. Only No. 2 Rafael Nadal,...