Roger Federer is a name that's been notably absent from tennis tournaments for the past nine months.
The 40-year-old, who has 20 Grand Slams to his name, last played competitively at Wimbledon in July 2021.
The Swiss star was knocked out in the quarter-finals after suffering a straight sets 6-3 7-6 6-0 defeat against Hubert Hurkacz.
That lopsided contest suggested something wasn't quite right with Federer - a reality he confirmed one month later.
“I just wanted to give you a bit of an update [on] what’s been going on since Wimbledon. As you can imagine, it’s not been simple,” Federer said in a video posted to Instagram in August 2021.
"I’ve been doing a lot of checks with the doctors as well on my knee, getting all the information as I hurt myself further during the grass-court season and Wimbledon.
“That’s just not the way to go forward, so unfortunately they told me for the medium to long term to feel better, I will need surgery. I decided to do it.
“I’ll be on crutches for many weeks and also out of the game for many months, so it’s going to be difficult of course in some ways, but at the same time I know it’s the right thing to do because I want to be healthy, I want to be running around later as well again and I want to give myself a glimmer of hope to return to the tour in some shape or form.
“I am realistic, don’t get me wrong. I know how difficult it is at this age right now to do another surgery and try it.
"But I want to be healthy, I will go through the rehab process I think also with a goal while I’m still active, which I think is going to help me during this long period of time.”
Federer has been sidelined since his knee surgery, missing both the US Open and Australian Open in the process.
As a result, the former world number one has seen his ranking fall to 26th as of late March.
When could Roger Federer play next?
Federer remains committed to playing tennis again and in March posted a video of him on the court with racket in hand.
Prior to the video being posted, it was confirmed that Federer would be representing Team Europe alongside Rafael Nadal at the Laver Cup in September.
"Super happy to be coming to London for the Laver Cup. It is always great to play tennis in front of all my British fans, with Team Europe and teaming up with my friend @rogerfederer," Nadal said in an Instagram post.
The 40-year-old may look to play again before then, however, with three Grand Slams scheduled to take place between now and his Laver Cup appearance.
The French Open begins in late May but the timing and clay-court surface means Federer may opt to sit out.
Wimbledon begins on June 27 giving Federer an extra month to get his body right and try to win a ninth title there.
Federer won his first grand slam at Wimbledon in 2003 making it a potentially fitting venue for his comeback.
Should he miss it though, he'd then have two more months of preparation before the US Open begins in late August.
Beyond that, it was confirmed in April that Federer will play at the Swiss Indoors in October - a tournament has won a record 10 times.
When could Roger Federer retire?
At the age of 40 and on the back of multiple knee surgeries, Federer knows his time playing professional tennis is nearing an end.
The Swiss icon wants to go out on his own terms, however, and stressed the importance of playing again before walking away from the sport.
"Even if I know that the end is near, I want to try and play some more big matches. That will not be easy, but I want to try," Federer told Tribune de Geneve in November last year.
"Let's be clear: My life is not going to fall apart if I don't play another Grand Slam final. But that would be the ultimate dream - to get back there.
"I want to see one last time what I'm capable of as a professional tennis player.
"I also wish I could say goodbye in my own way and on a tennis court. That's why I give my all in my rehabilitation."
Based on those comments, whenever Federer does play another Grand Slam, there's every chance it could well be his last.
