By Richard Pagliaro | Tuesday, September 20, 2016

Serena Williams' quest to regain the world No. 1 ranking may have to wait.

The 34-year-old Williams, who lost her world No. 1 ranking to Angelique Kerber following her US Open semifinal defeat to Karolina Pliskova, is uncertain about her status for the rest of the 2017 season.

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The world No. 2 told CNN she isn't sure if she will play again this season as she focuses on regaining her health. Williams was pained by a left knee injury during the US Open.

"I don't know. I'm definitely taking it a day at a time," Serena told CNN when asked if she will play again in 2017. "I'm tired of playing tennis unhealthy and taking losses that I would never lose. I definitely want to make sure I'm healthy and playing at my best or at least 80 percent healthy or 70 percent healthy.

"That way I can be able to play at a higher level."



Williams, whose Open Era record-tying streak of 186 straight weeks as world No. 1 came to an end with the defeat, said a left knee injury she suffered in the second or third round hindered her movement in Flushing Meadows.

"I have been having some serious left knee problems," Williams said. "I wasn't tired. Fatigue had absolutely nothing to do with it. If I was tired I should definitely get into a new career.

"I wasn't able to move the way I wanted to move. When you're injured you're thinking of other things when you should be just playing and thinking of your shots. My mind was just a little bit everywhere. But it was what it was."

In the aftermath of her US Open semifinal loss, Williams' coach, Patrick Mouratoglou, told ESPN "it's obvious she's injured."

"To me it's obvious she's injured," Mouratoglou said immediately after the match. "We knew she had knee pain yesterday. We hoped it would be okay tonight but it was not. I don't remember the last time (she was healthy).

"At the end I knew the knee was hurting. (She was) 70 percent compared to what she usually does. Maybe she's gonna be able to overcome that and play, but clearly she was not. Even from the start she was not moving at all so that is difficult to play tennis. We have to know what's happened to her knee."

Williams, who celebrates her 35th birthday on September 26th, shut down her 2015 season following her stunning US Open semifinal loss to Roberta Vinci.