http://www.youtube.com/watch?v=zh6w9zxOdFY

Serena Williams, 31, came back to beat Petra Kvitova 3-6, 6-3, 7-5 to advance to the semifinals of the Qatar Open and will overtake Chris Evert as the oldest woman to hold the WTA No. 1 ranking since the computer rankings were introduced in 1975. This will be Williams' fifth stint at No. 1, having first ascended to the spot in July 2002 and most recently holding it for 49 weeks from November 2009 to October 2010. It will be her 124th week total at the top.

Serena had spent the week downplaying her desire to recapture the No. 1 ranking. After winning her third-round match Thursday, she was asked whether it was on her mind and practically rolled her eyes.

"Not really," she said. "I'm so over it. Everyone else is thinking about it."

On Friday, after firing an ace down the tee on match point, Williams dropped to her knees and offered up a celebration rarely seen outside of a Slam final, overcome with tears and emotion. How much had the No. 1 ranking been weighting on her mind? When asked to sign the camera, she had one simple message: "Serena is #1"

"I’m so sensitive nowadays; I’m always crying," she said on court, her voice quavering. "But I never thought I would be here again. I’ve been through so much."

Serena says her emotional on-court reaction surprised her. "I didn't imagine that it meant that much to me. I did not expect to not be able to stop crying. I didn't expect to feel that way at all I just thought I would be happy and, you know, just move on to the next round. But my reaction was completely unexpected from me."

Her last reign at No. 1 was ended by a foot injury she sustained after winning Wimbledon in 2010, which led to a pulmonary embolism, a complication from her surgery. Her comeback from those ailments finally got traction last year after suffering a shocking first-round loss to Virginie Razzano at the French Open, her first first-round loss at a Slam in her career. Since, Williams has lost only two matches (Angelique Kerber in Cincinnati, Sloane Stephens at the Australian Open) and won two Slams, Olympic gold and the WTA Championships. Now that she's back on top of the rankings, the comeback is complete.

"I didn't want to get into talking too much about No. 1," she said after the match. "I think I would have put too much pressure on myself, like it's here, and everyone is, All you have to do is get to the semis. And, you know, I do have tough matches to play."

Serena's not done yet in Doha. She'll play Maria Sharapova in Saturday's semifinals. If Sharapova wins she'll return to No. 2 and the current No. 1, Victoria Azarenka, will drop to No. 3. While Serena is in the best position to hold on to the ranking through the French Open because she has the fewest number of points to defend , but that doesn't mean she's 100 percent safe. Here's a look at the significant results all three women are defending through Roland Garros.

• Serena: Titles - Charleston, Madrid; Semifinalist - Rome

• Azarenka: Titles - Indian Wells; Finalist - Stuttgart, Madrid

• Sharapova: Titles - Stuttgart, Rome, French Open; Finalist - Indian Wells, Miami; Semifinalist - Madrid

"Everyone's trying and playing so well and so consistent, and no one is really losing early," Serena said, remarking on a week that's seen the Top 4 women make the semifinals in Doha. "You know, there are two top players that are just playing so well, and more than that, so consistent.

"It's not as lonely as it looks at the top."

Here's a quick look at some of the Twitter reaction to Serena's emotional win.

https://twitter.com/MattBarbarin/status/302503277277356032

https://twitter.com/darren_cahill/status/302484746024398849

https://twitter.com/bgtennisnation/status/302487143417253888

https://twitter.com/christophclarey/status/302485853899481089

https://twitter.com/Venuseswilliams/status/302494206889431040

https://twitter.com/BigSascha/status/302486035491868673

https://twitter.com/serenawilliams/status/302488916450242560