Hingis announces her retirement at the WTA Finals

Martina Hingis has announced her retirement on Facebook. The 37-year-old's final tournament will be the WTA Finals in Singapore, where she and Yung-jan Chan are the top seeds. The duo won their opening round on Thursday over Anna-Lena Gronefeld and Kveta Peschke.

"Looking back now, it's hard to believe that almost exactly 23 years ago I made my professional debut," Hingis wrote. "The years that followed have been some of the most rewarding years of my life, both personally and professionally, but I believe the time has come for me to retire, which I will be doing after my last match here in Singapore."

Chan and Hingis are co-No. 1's and have won nine titles together since first pairing up in February. They won the US Open for their first Grand Slam together. It marked Hingis' 25th career Grand Slam crown.

During her career, the Swiss has won 42 singles WTA titles including five Grand Slams. In doubles, she has won 20 majors (13 in doubles and seven in mixed doubles).

Once a teenage prodigy, Hingis reached No. 1 as a 16-year-old in 1997, two months after becoming the youngest-ever singles Grand Slam champion at the Australian Open. She would win two more Grand Slams that year (Wimbledon and the US Open) and reach No. 1 in doubles for the first time in 1998.

It will be Hingis' third career retirement. She first stepped away from the game as a 22-year-old in 2002 after injuries to both ankles. After returning in 2006, Hingis again retired after a hip injury and positive test for a metabolite of cocaine in 2007. Just when it seemed like Hingis had left the game for good, she came out of retirement once more in 2013 as a doubles specialist.

Since then, Hingis' final renaissance has seen her win 10 of her Grand Slam titles (four in doubles titles and six in mixed). With Sania Mirza, she won the WTA Finals in 2015 (for her third career year-end doubles title) and with Timea Bacsinszky, she won a silver medal at the Rio Olympic Games.

"This isn't a goodbye," Hingis wrote. "As history shows, I haven't been able to stay away from tennis for long in the past, and I am looking forward to seeing what new opportunities and challenges lie ahead of me."

Hingis and Chan face Timea Babos and Andrea Hlavackova next.

5

Singles Grand Slam titles

7

Mixes doubles Grand Slam titles

13

Doubles Grand Slam titles

43

Total WTA singles crowns

64

Total WTA doubles crowns

• Youngest-ever Grand Slam singles champion at the '97 Australian Open (16 years, three months)

• Youngest-ever No. 1 in history (March, '97)

• Ranks fifth on the most weeks at singles No. 1 list with 209

• Fourth woman in history to win the calendar-year doubles Grand Slam ('98)

• Third woman to hold the No. 1 ranking in singles and doubles at the same time ('98)

• Returned to No. 1 in doubles in October, 19 years after first reaching the top