Federer out of tennis till 2021 after surgery

Twenty-time Grand Slam champion Roger Federer said he will be sidelined until 2021 after undergoing his second knee operation in a matter of months. The Swiss said he underwent follow-up arthroscopic surgery "a few weeks ago" after undergoing a similar keyhole procedure in February. "I plan to take the necessary time to be 100 percent ready to play at my highest level," he said in a statement.