No.1 seed Jessica Pegula prevailed in an all-American second-round thriller at the Credit One Charleston Open on Tuesday, battling past Amanda Anisimova 3-6, 6-4, 7-6(3).

To squeak her way into the Round of 16, World No.5 Pegula needed 2 hours and 26 minutes to fend off a stern challenge from Anisimova, a former Top 25 player currently ranked No.264.

"It's always a tough one playing Amanda, because she is just a really great ball striker, and she can really take the racquet out of your hands," Pegula said, after surviving the battle. "So you know when she's hot, it's really tough.

"I just had to buckle down, and I think I started being a little bit more active with my feet and pressuring her a little bit more, and being able to move her and scrap out a few points as well. I just kind of found a way today, but it was a really great match, I thought, especially the last set was super high-level."

Fast facts: Pegula had defeated Anisimova in their only previous encounter, which was a straight-sets affair at the 2020 Western & Southern Open in New York City. Moreover, Pegula had not lost to a player ranked outside the Top 100 since last summer, when she was upset by Taylor Townsend in Rome.

Anisimova nearly upended both of those factoids, pushing Pegula down to the wire, but the top seed eventually eked out her first clay-court match-win of the season. Pegula is now one step closer to matching or bettering her career-best Charleston semifinal appearance from last year.

"I think during the tiebreak, [the key] was just trying to not get upset, not get too negative if something went wrong," Pegula said. "I just kind of played every single point.

"But I think for me, especially with how well she returns, I really wanted to focus on my serve, especially in the third [set], and not let her get too many chances, which I did a good job of."

Key moments: Anisimova’s power game was peaking in Tuesday's first set, where she hit 15 winners to Pegula’s six. Anisimova had not played an event since January, but at the start of the match, she brought the form that propelled her into the Australian Open Round of 16 earlier this year.

However, Pegula’s impeccable defense made a bulk of the difference in the second set, where she broke Anisimova at love at 5-4, leveling the match at one set apiece.

The clash came down to the third set, where the pair exchanged breaks early and neither could barrel ahead. Pegula held her first match point at 5-4 on the Anisimova serve, but the unseeded player erased that with a passing winner.

Katelyn Mulcahy

Naturally, the intense battle was settled with a final-set tiebreak. Pegula leapt in front, grabbing five more match points with a backhand winner for 6-1.

Former Roland Garros semifinalist Anisimova found two incredible backhands of her own to reach 6-3 and give herself hope of a comeback, but she misfired on a forehand on the next point, ceding the match to Pegula before a hug at the net between the compatriots.

"You don't want to go to [Anisimova's] backhand," Pegula said. "Her backhand is money. I always say I think she has the best backhand on tour. At least, when everyone asks me like which shot would you pick from each player, I usually say her backhand."

The match ended with Anisimova having 12 more winners than Pegula, but also 23 more unforced errors. Each player broke serve four times in Pegula’s narrow win.

Next up: Pegula will now face Poland's Magda Linette in the Round of 16. Linette pulled off a come-from-behind win of her own on Tuesday, upsetting No.13 seed Dayana Yastremska 0-6, 6-4, 6-3.

Pegula defeated Linette in straight sets in their only previous meeting, on the hard courts of Miami last year.