Roger Federer out of Western Southern Open

Roger Federer withdrew from the Western Southern Open due to a knee injury one day after Naomi Osaka said she wouldn't play in the event.

The final tune-up for the U.S. Open wraps eight days prior in Cincinnati and is a popular stop, and Federer and Osaka remain entered in the Grand Slam the following week at Flushing Meadows.

Federer, 39, is a seven-time champion of the WSO but event organizers said Thursday they rece