After brilliant 2015 run, is Serena Williams’ encore already in jeopardy?

Serena Williams has dominated women’s tennis for so long, it’s hard to believe that last year might have been her best yet on tour.

She spent the entire year ranked No. 1, winning the Australian Open, the French Open and Wimbledon along the way in a Grand Slam bid that fell just short with a loss in the semifinals of the U.S. Open.

That run brought her to 21 major titles, good for third all-time. She was also named AP’s Female Athlete of the Year for the fourth time — far outpacing the likes of Carli Lloyd and Ronda Rousey. And all this in the year she celebrated her 34th birthday.

Unfortunaly, her 2016 is off to a rocky start.

SERENA'S GRAND SLAM WINS

Williams is in Australia for the Hopman Cup, an international, mixed-gender, team competition that also serves as a tune-up for the Australian Open.

Thing is, she hasn’t been able to do much tuning up. She skipped her team’s opening loss to the Ukraine on Monday with inflammation in her left knee. Then on Tuesday, she withdrew from her match against Australia’s Jarmila Wolfe, trailing 7-5, 2-1 at the time.

On Wednesday, she officialy withdrew from the tournament, with Vicky Duval serving as her replacement.

While there hasn’t been much news about the extent of the injury, it has to be concerning considering the Australian Open starts on Jan. 18 — less than two weeks away.

One thing she does have going for her? All that success in 2015 didn’t come easy. She came came close to being knocked out at Wimbledon and at the French Open (multiple times) but somehow managed to recover every time.

Here’s hoping she recovers in time for the year’s first major because it just won’t be the same without her in it.