NEW YORK -- Jessica Pegula made her Grand Slam main draw debut in 2015 at the US Open. Ranked No.260, she qualified on her own merit at 21 and earned her first win, a straight-set win over Alison Van Uytvanck. 

She did not win a Grand Slam main-draw match for another five years. 

Now she's the World No.3, the highest-ranked American on either the ATP or Hologic WTA Tour, and one of the toughest outs in tennis. She has made the quarterfinals of all four Grand Slams, including five of the last seven. 

US Open 2023: Draw Order of play | Scores | 411

On Thursday, she eased into the third round of the US Open with a 6-3, 6-1 win over Patricia Maria Tig. The win is her 60th on hard court since the start of 2022, a number beaten only by World No.1 Iga Swiatek's 75. Among the deep bench of American women, only Serena and Venus Williams have managed as many hard-court wins over a two-season span in the last decade. 

Now 29, Pegula can only shake her head in bemusement when she thinks about how far she's come. 

"When I look back at some of my old matches when I was younger, I'm, like, what was I even thinking," Pegula said this week. "I don't know what I was doing, because now it's so much different.

"Honestly, I probably just played really stupid when I was younger. I just didn't play smart at all. I was completely the opposite of what everyone thinks I am now, which is hilarious."

More from Day 4: Jabeur battles through | Sabalenka, Vondrousova cruise Svitolina advances

Who does everyone think Pegula is now? In the locker room, she's an unflappable and reliable voice of reason. On the court, she brings a level of consistent, high-level baseline tennis that few can match. As her colleagues and competitors quickly point out, she is the unflashiest billionaire they could imagine. 

"I'm a big fan of Jess because this is the girl who could just relax but is one of the most hard-working girls on tour," said Daria Kasatkina. She remembers her first run-in with Pegula at an ITF tournament in 2015.

"She's playing singles, doubles, every single week. She is here from the morning to the late evening and she's always, from the outside, the same."

"Jess is an inspiration for the younger kids. She loves tennis so much -- otherwise, I don't know why she's playing singles and doubles every single week."

- Daria Kasatkina

It seems every player has an ITF story with Pegula. Taylor Townsend remembers playing doubles with Pegula a decade ago on the lower levels. 

"We were grinding 25Ks," Townsend said. "She didn't take the easy way. She didn't skip steps. So it's a reason that she's here. It's a reason that she's having the success that she has.

"I have so much respect for people like that because you do the dirty work to get to the shiny thing."

Pegula has certainly won some shiny things. Last year it was the WTA 1000 in Guadalajara. A few weeks ago, she bagged another WTA 1000, this time in Montreal, defeating Swiatek and Coco Gauff along the way.

But Pegula knows the one trophy missing from her cabinet is the one everyone is obsessed with: a Grand Slam. Consistency just isn't flashy enough for some.

"I see people online and they're like, 'How is she No.3?' And I'll see someone reply, 'Because she just wins a crap-ton of matches'," Pegula said.

"I just don't lose in the first round like other girls. Maybe they win a 1000 or a Slam, but I also made the quarters of the last 10 tournaments. It gets lost in the mix because people prioritize one thing, but I think it's an achievement that I've been able to be so consistent for a couple of years now."

Her competitors agree. When 2022 Wimbledon champion Elena Rybakina was asked which was harder, winning a Slam or consistency, the World No.4 pointed to the latter.

"I think to be consistent, it's very tough," Rybakina said. "Just to be consistent with all the changes of the surface, balls, traveling a lot, I would say this is the toughest."

"It's so crazy. I never thought that consistency would be my M.O."

- Jessica Pegula

Pegula can acknowledge the irony. She only cracked the Top 100 four years ago. The first time she made the second week of a major came just over two years ago at the 2021 Australian Open. It's been a late but rapid rise for the American, which makes her ability to hold her level even more impressive.

"When I came on tour I struggled with consistency. I struggled with putting back-to-back wins together, back-to-back tournaments. When I was 22, consistency was nowhere even mentioned along my name or my game. 

"So it's a personal achievement. I'm winning matches and doing well. It's what you want in your career, to have some form of success. If it comes with being very consistent and winning a lot of matches, hell yeah, I'll take it."

Nine months into the season, Pegula has held her ranking. She began the year at No.3 and, after getting nudged out of the Top 3 by Rybakina, she's back. She did it by making the Round of 16 or better at all but two tournaments this year.
 
"Some people think about Slams and whatever, but trying to sustain a ranking is also very difficult," Pegula said. It's a different achievement but it's still pretty cool."

Pegula, Parks among WTA stars at Come Play youth clinics