Who is the men's tennis GOAT? It's a fair question. There are multiple claimants to the throne, but as he leaves the sport behind, it's fair to say the retiring Roger Federer will be mentioned among the very best for the decades to come.
It's not hard to see why. The Beijing 2008 Olympic gold medallist in doubles ranks among the top three in tennis history in nearly every major metric – tournaments won, Grand Slam titles, weeks at world number one, and more.
The 41-year-old calls time after a 24-year career that saw him make his ATP tournament debut at 17 in 1998 before his first Grand Slam main draw the year later. Along the way, he won 20 Grand Slams including eight on the hallowed grass at Wimbledon, and broke all kinds of records.
We take a look at some of the incredible numbers that underpinned Federer's career.
Roger Federer at Grand Slams
When Federer beat Marin Cilic at the 2018 Australian Open, the Swiss became the first man to win 20 majors. His 20 wins have come from 31 final appearances, second to only Novak Djokovic; Federer also holds the record for most Grand Slam semi-finals (46) and quarter-finals (58) from his 81 tournaments.
No man has appeared in more majors in the Open Era, with Spain's Feliciano López sharing the record with Federer at 81. In those 81 tournaments, Federer won 369 matches, another stat in which no-one has surpassed the Swiss. When he won his 100th, he became the first men's singles player to do so in the Open Era.
His 20 titles breaks down as follows: eight at Wimbledon, six at the Australian Open, five at the US Open, and one at the French Open. His win at Roland-Garros in 2009 completed the career Grand Slam, while his eight Wimbledon crowns is also a men's record.
DIVE DEEPER: Federer's Grand Slam career in numbers
Federer's record streak as world number one
Federer's longevity has given rise to many records related to streaks, not least his consistency as the world number one.
The Swiss spent 310 weeks of his career ranked as the world's best, a number behind only Djokovic (373). However, of those 310, no-one knocked Federer off the top for 237 straight weeks. That's more than four and a half years.
Aged 22, Federer first reached the peak of the rankings on 2 February 2004, not relinquishing the spot until 18 August 2008. He was last ranked number one for a week in June 2018.
In that span, Federer won five straight US Open titles – no one else, man or woman, has done so in singles in the Open Era. He also won five consecutive Wimbledon crowns from 2003 to 2007.
The Swiss also reached 10 straight finals at the Slams during his first streak as world number one, from Wimbledon in 2005 through to the US Open in 2007 before losing in the semis at the 2008 Australian Open.
READ MORE: Roger Federer's Wimbledon finals
Roger Federer's ATP career: 103 singles titles
Federer leaves tennis having won 103 ATP singles titles, which aside from his 20 majors also includes 28 ATP Masters and six ATP Finals crowns.
The first of those 103 came at the Milan Indoor in February 2001, where he beat Julien Boutter of France in his third career ATP Tour singles final.
From the 2003 Vienna Open to the 2005 Thailand Open, Federer won 22 consecutive ATP singles finals that he reached.
His last ATP Tour title came on home soil at the 2019 Swiss Indoors, when he defeated Australia's Alex de Minaur for his 103rd career title.
READ MORE: Federer's post-retirement plans
Olympic champion Roger Federer: his international career
Roger Federer is an Olympic champion in his own right. His eighth and final ATP Tour doubles title came at the Olympic Games Beijing 2008, when he and Wawrinka won gold for Switzerland.
The pair beat Sweden's Simon Aspelin and Thomas Johansson in four sets in the Chinese capital to clinch gold in Federer's third Olympic Games appearance.
In his Olympic career, Federer racked up a 20–7 record across singles and doubles.
Federer also played 70 Davis Cup rubbers for Switzerland, winning 52 of them. He was part of 19 match wins for the Swiss team, including during their Cup-winning run in 2014.
He also won three Hopman Cup titles representing his country, compiling a 27–9 record across his singles and mixed doubles rubbers.
All numbers that contribute to the GOAT debate.