Four-time Grand Slam winner Kim Clijsters has announced she will return to professional tennis in 2020, marking her second comeback to the sport.

The 36-year-old, who hasn't played professionally since 2012, announced the news on Twitter:

Clijsters first retired in 2007 due to a series of lingering injuries, but she returned in 2009 and shocked everyone by winning the U.S. Open just months after her first competitive match back.

She would win the final Grand Slam of the year three times in total, as well as the 2011 Australian Open.

News of her second comeback came out of nowhere and shocked the tennis world.

Tennis writer David Law thought he was being fooled:

A mother of three, Clijsters said she was inspired by others in her position, per the Guardian:

Former rival Serena Williams gave birth to a daughter in 2017 and has since played in four Grand Slam finals. Clijsters won three of her four Grand Slams after giving birth to her first child, a daughter, in 2008.

At the age of 36, she will have to overcome the odds to add a fifth Grand Slam crown to her resume.

Tennis writer Enrico Maria Riva noted the new generation of stars is remarkably young:

There are reasons to believe Clijsters could find success again, however. The likes of Naomi Osaka, Ashleigh Barty and Bianca Andreescu won their first Grand Slam title in the last two years, but the top players have all struggled with consistency, and none of them have dominated. There hasn't been a single player who won two Grand Slams in one year since Angelique Kerber in 2016.

On top of her four Grand Slam triumphs, Clijsters won the WTA Tour Championships three times and is a former World No. 1.