(CNN) -

Caroline Wozniacki has had her critics in the past. A defensive game and not landing a grand slam title while she was ranked No. 1 provided fodder for her detractors.

But now everyone, it seems, is rooting for the Dane.

Why? Well, much of it must be down to the fact that Wozniacki was dumped -- and very publicly -- by golf sensation Rory McIlroy only months before they were due to tie the knot.

McIlroy ended the relationship in May, saying he wasn't ready for marriage, and the news left Wozniacki devastated.

She was visibly distraught as she spoke to reporters at the French Open soon after, and exited in the first round, her earliest loss at Roland Garros in seven years.

The Northern Irishman has since rediscovered his vintage form, claiming he is more focused, and has won two major titles and regained his No. 1 ranking.

Wozniacki has also picked up her game after a lengthy slump.

She's the favorite to reach the U.S. Open final from the bottom half of the draw after upsetting Maria Sharapova on Sunday. And whereas Wozniacki said earlier in 2014 she would like to become a young mother -- suggesting her tennis days were numbered -- her own focus is now solely on the court.

That Wozniacki is prospering in New York is slightly ironic -- it was where she was reportedly supposed to marry McIlroy in November. She's sure to return to the Big Apple that month, however, having decided following their split to run in the New York City Marathon.

Wozniacki has so far refused to discuss her relationship with McIlroy at the U.S. Open, not that any of the fans minded.

The crowd at Arthur Ashe Stadium in her match against Sharapova was firmly behind the 24-year-old, leading her to gush afterwards: "The crowd was amazing today."

Her victory over Sharapova put Wozniacki into a first grand slam quarterfinal since the 2012 Australian Open.

"The season for me has been a little bit up and down," Wozniacki said. "And it's so nice to kind of start feeling like I'm playing the way I want to.

"This hard-court season has been amazing for me. I actually started already feeling really good on court since Eastbourne (in June). I have just been building on my game since then."

Wozniacki won a title in Istanbul in July and even though she didn't add to her haul in Montreal and Cincinnati, the player that stopped her was world No. 1 Serena Williams. Both of their encounters went to three sets.

They have become good friends this year, spending time together in Miami after their early departures from the French Open.

Although Wozniacki still can't be considered an attacking player, her serve has improved, and she has become more aggressive on the baseline.

Her retrieving, though, is still what gives opponents problems. Making Sharapova keep running paid off, as the Russian committed 43 unforced errors.

"I think she's better at what she's done really well in her career," Sharapova said. "I think she's moving extremely well; she's fit.

"I mean, she's always been fit, but there is a little bit more on her defense shots.

"It's not just balls up in the air. She's doing a little bit more with them."

Wozniacki faces another counter puncher, Sara Errani, in the last eight on Tuesday, and could face Williams -- again -- in the final. Williams advanced to the quarterfinals Monday by beating Estonia's Kaia Kanepi 6-3 6-3.

"I have had a great summer, and I told Serena I'm pretty tired of her," said Wozniacki. "I said, 'Can you just get out of my way?'

"We just laugh about it. This one was a great win for me. Maria, again, is a good player. For me, I think mentally as well to get that in my pocket is kind of nice.

"I still have hopefully a few good matches in me here in this tournament."