Critics said Taylor Townsend was too heavy. She couldn’t win big matches. Her game wasn’t good enough. Now she is being called something else at the US Open: giant killer.

The 23-year-old American captured the biggest victory of her career on Thursday, defeating Wimbledon champion Simona Halep 2-6, 6-3, 7-6 (7/4) to reach the third round at Flushing Meadows with her first triumph over a top-10 opponent after 10 prior losses.

“This was a huge, monumental moment,” Townsend said. “It was a very defining moment for me to realise that I belong here. I’ve had a lot of people doubting me being able to break through. It’s just confirmation more for myself that I’m on the right path, doing the right things.”

The 116th-ranked qualifier, who matched her deepest Grand Slam run from her debut at the 2014 French Open, broke into tears on the court after the match.

“This means a lot. It has been a long journey,” she said, wiping away tears.

Townsend will next face another Romanian, 106th-ranked Sorana Cirstea. She squandered a match point at Wimbledon and lost to Dutch fourth seed Kiki Bertens in the second round, a loss that literally woke her in the middle of the night.

“Just to be able to get over the hump, it’s such an amazing feeling because after Wimbledon, I was devastated after I lost to Bertens after having a match point,” she said.

“That woke me up out of my sleep. Oh, dropshot. I put my head down and just worked really hard and just tried to take the positives from it, just continue to press forward.”

In 2012, the US Tennis Association asked Townsend, then the world’s top-ranked junior woman, to skip the US Open girls tournament because of her weight and denied her request for a wildcard into the US Open.

Townsend paid her way to qualifying, didn’t make the girls field and dropped USTA coaching. She’s now coached by family friend Donald Young Sr.

“It’s really hard to deal with that stuff when personal issues are publicised,” Townsend said.

“It has been a long road. A lot of haters, a lot of people who weren’t sure. I’ve heard it for a really long time that I was never going to make it, that I wasn’t going to be able to break through or do this or do that.

“Especially over this last year, I’ve really embraced that, being able to prove people wrong. I thrive in these kind of conditions and I think it showed today.”

No major sponsor help

Townsend, who read a book with notes to help her focus during changeovers, has not received the big-money sponsor support as many other rising US talents have, which has limited her to European trips only to Grand Slam events.

“I don’t have a whole bunch of sponsors knocking down my door giving me money. A lot of the stuff is coming out of my pocket,” she said.

“So I have to be very financially smart with where I go, where I travel, what makes sense because this is a very expensive sport. A lot of people don’t really see that side of it.

“I have to go and do things that are financially advantageous. Is it smart to go to Europe for 12 weeks in quallies where you make $900 if you lose first round and your flight was $3,000 to get there? You can do the math.”

But it hasn’t taken a plane ticket for Townsend to find herself.

“I know who I am. I know what makes me tick. Sometimes it works, sometimes it doesn’t. You dust yourself off and you keep going,” Townsend said.

“I think for some years I was lost, lost in a sea of a lot of stuff. But it’s nice to be able to come up to the surface and float, eventually swim.”

And critics roll off her back like water.