GENEVA, Switzerland (AFP) — Roger Federer will retire following next week’s Laver Cup after admitting his battles with a knee problem had forced him to call time on his historic tennis career. Tributes poured in for the 41-year-old Swiss legend from rivals such as Rafael Nadal, while Serena Williams welcomed him to the “retirement club”. Federer, a winner of 20 Grand Slam titles and one of the best players of all time, has been […]