Roger Federer is resigning from proficient tennis at age 41 after a progression of knee tasksn  text

Federer closing a career in which he won 20 Grand Slam titles, finished five seasons ranked No. 1

"I am 41 years old. I have played more than 1500 matches over 24 years.

Federer's 20 Grand Slam titles rank third all-time among men's players

Federer, Nadal, Djokovic and Andy Murray are set to play together for the first time when they compete Sept. 23-25

Federer's records include being the oldest No. 1 in ATP rankings history

FiFederer leaves with 103 tour-level titles on his substantial résumé and 1,251 wins in singles matches

Federer won his first Grand Slam title at Wimbledon in 2003,

Federer would go on to blow way past that, ending up with 20 by winning eight championships at Wimbledon

Federer and his wife, Mirka  a tennis player too; they met as athletes at an Olympics -- have two sets of twins.