US Open champion Bianca Andreescu has pulled out of the Australian Open because of a knee injury.

The 19-year-old, who beat Serena Williams at Flushing Meadows in September to win her first Grand Slam, will not be in Melbourne for the sport’s opening top event of 2020 due to a problem she suffered during last year’s WTA Finals.

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Australian organisers also revealed on Saturday that Juan Martin del Potro and Richard Gasquet had withdrawn because of knee problems.

The tournament gets under way in Melbourne on January 20.

Andreescu tweeted: “Hey guys, just wanted to give you a little update on my knee rehab after I got injured at the WTA finals in Shenzhen.

Open is unfortunately too soon in my rehab process and I sadly will not be able to play in it this year. It was a very tough decision to make as I love to play in Melbourne but I have to respect the recuperation plan for my knee and body. I can’t wait to come back to Aus soon x

— Bianca (@Bandreescu_) January 11, 2020

“My rehab is going well, I feel better and stronger every day but after discussing it with my team and following the recommendation of the doctors, the Australian Open is unfortunately too soon in my rehab process and I sadly will not be able to play in it this year.