Tennis is one of the most physically demanding sports. The game itself requires a lot of running and it is often played in stifling hot temperatures, with players wearing heavy clothing. Tennis is not an easy sport to play at the highest level for an extended period of time, so when do these athletes decide to hang up their racquet?

Roger Federer is arguably the greatest male tennis player to ever live. He has won more than 900 ATP tour matches in his career and held both the No 1 ranking in the world for 302 weeks during 2005-2007 and 2009-2017. At 37 years old, he seems as though he could compete on tour for another decade or longer. If anyone deserves retirement, it is Federer, but it seems as though retirement is the last thing on his mind. The Swiss player has qualified for the upcoming Australian Open and will be entering what could be his 26th career Grand Slam appearance, more than any other man in history. Federer’s success on tour and longevity shows that he is one of a kind and perhaps we won’t see another like him anytime soon.

Maria Sharapova suffered from injuries throughout her career which cut short some of her seasons. Her latest injury came after an incident at a restaurant where she was reportedly given meldonium without knowing it (a substance that was banned by the World Anti-Doping Agency). She was initially handed a two-year suspension but that was reduced to 15 months on appeal with some arguing that her mistake didn’t warrant such a lengthy sentence. Sharapova returned to the tour in 2017, but most of her ranking points were deducted and she had no ranking when she came back. She won two small tournaments, Porsche Tennis Grand Prix in Stuttgart and Tianjin Open in China with ease against weak fields. The next part of her return will be playing qualities at the upcoming Australian Open, where she is expected to play Mona Barthel of Germany’s first round.

And then there is Serena Williams who has been through it all throughout her career. Considered by many as being one of the greatest athletes ever competing in a global sport, she has had her highs and lows on tour. She has won 23 Grand Slam titles; broke the all-time record for most weeks at No 1 in women’s tennis history, and is a four-time Olympic Gold medalist. In recent years, Serena has been dealing with health issues including blood clots that have kept her out of action for over a year.

Serena has been training rigorously in South Florida but many have wondered when she will return to the court. During an interview earlier this month, Serena stated that she plans on playing in 2018 and would love to play Federer if he decides to keep going past the age of 37. The American says that she is taking things day by day but does not have a set return date.