Maria Sharapova retires from tennis after 28 years of playing

Five-time Grand Slam champion Maria Sharapova has announced her retirement.

"Tennis -- I'm saying goodbye," she wrote in an essay that appeared in Vogue and Vanity Fair.

Sharapova turned pro in 2001 at age 14. She won Wimbledon in 2004, the US Open in 2006, the Australian Open in 2008 and the French Open in 2012 and 2014.

The 32-year-old Russian reached No. 1 in the WTA rankings in 2005, 2007, 2008 and 2012, but she has dropped to No. 373. She lost in the first round of this year's Australian Open to Croatia's Donna Vekic in straight sets.

"Throughout my career, Is it worth it? was never even a question -- in the end, it always was," she wrote. "My mental fortitude has always been my strongest weapon. Even if my opponent was physically stronger, more confident -- even just plain better -- I could, and did, persevere.

Sharapova received a two-year suspension by the International Tennis Federation in 2016 for testing positive for the banned substance meldonium. The suspension was reduced to 15 months by the Court of Arbitration for Sport after Sharapova appealed. The CAS said there was "no significant fault" by her.

"In so many ways, I feel like something I love was taken away from me and it will feel really good to have it back," Sharapova said in a statement after her successful appeal.

Shoulder injuries hampered her career, and she had multiple surgeries.

Sharapova compiled a 645-171 singles record that included 36 titles.