Coco Gauff rallied from a break down in the final set to beat Swede Rebecca Peterson 6-3, 1-6, 6-4 and reach the Indian Wells quarter-finals for the first time on Tuesday.
After taking the first set, the sixth-seeded American began to struggle with her forehand in the second and an opportunistic Peterson began to apply pressure by coming into the net.
But after suffering an early break in the decider, Gauff stepped up her defence, fending off three break points at 4-4 and breaking Peterson for a fourth time on match point to book her spot in the last eight.
Gauff, who turned 19 on Monday, was serenaded with a rendition of "Happy Birthday" after the match by the partisan crowd in the Southern California desert.
"Today, it was just a mental thing, staying in the match," Gauff said.
"I wasn't playing my best in some moments and wasn't serving as well as I'd like to, but I think my mentality kept me in today."
Next up for Gauff is a meeting with Belarusian second seed Aryna Sabalenka, who survived a second-set scare to beat 16th seed Barbora Krejcikova 6-3, 2-6, 6-4.
Sabalenka sent down 11 aces in the match to secure victory and get revenge on the Czech, who beat her at last month's Dubai Tennis Championships.
Elsewhere, seventh seed Maria Sakkari outlasted big-serving Czech Karolina Pliskova 6-4, 5-7, 6-3 in a two-hour and 45-minute marathon to reach the quarters.
With the win the Greek keeps alive her hopes of capturing a first Indian Wells crown after making the final last year.
Sakkari will next face Czech 15th seed Petra Kvitova for a semi-final spot, after the two-time Wimbledon champion saved four match points en route to a 6-2, 3-6, 7-6(11) win over third-seeded American Jessica Pegula.
"I play for these emotions," Kvitova said after the epic encounter.
"The match was up and down, a disaster at times. I knew that Jessica will not miss, but I still had to go for it. I think this might be one of the best matches I played..."
World number one Iga Swiatek continued her Indian Wells title defense with a 6-3, 6-1 victory over Emma Raducanu on Tuesday to set up a quarter-final against unseeded Romanian Sorana Cirstea.
Swiatek came under pressure early in the opening set but some clean ballstriking helped her hold for a 3-2 lead after two tight service games. She raised her level further to break Raducanu in the next game before pulling away.
Having wrapped up the first set when Raducanu sent a shot long from the baseline, Swiatek grabbed an early break in the second to heap the pressure on the Briton, whose unforced errors began to mount.
Swiatek, bidding to become only the second female player to successfully defend the Indian Wells title after Martina Navratilova in 1990-91, raced to a 5-1 lead playing flawless tennis and running her opponent ragged.
The US Open champion closed out the win when Raducanu struck the net on serve in a tame end to her fine run in the Southern California desert.
Medvedev overcomes injury and Zverev to reach quarters
Daniil Medvedev shook off a mid-match ankle injury to reach the Indian Wells quarter-finals with a gutsy 6-7(5), 7-6(5), 7-5 victory over Germany's Alexander Zverev on Tuesday, extending his winning streak to 17 matches.
It was an impressive effort from the fifth-seeded Russian whose tournament appeared over when he crashed to the court in the second set with what initially appeared to be a serious ankle injury.
While Medvedev was able to continue and advance to the Indian Wells last eight for the first time, he said that he now expected to feel considerable pain and would likely have a scan on the ankle to assess the damage.
"Now when the adrenaline goes down the body cools down it is going to be pretty painful and I am going to probably do a scan to see what it is and if I can continue to play," said Medvedev, winner of three straight tournaments in Rotterdam, Doha and Dubai.
Down a set and on serve at 3-2 in the second, Medvedev turned over his ankle attempting to make a return and winced in pain as the trainers, Zverev and the tournament supervisor all rushed to his side as he clutched his right leg.
Once back in his chair, Medvedev had the ankle heavily taped and then returned to the court hobbling, but determinedly forcing the second set to another tiebreak.
This time, the 27-year-old Russian prevailed 7-5 to send the contest to a third set.
"When I twisted it I thought I am going to stand up just fine and then the pain started growing very fast and I thought, 'Oh, that's not a good sign,'" Medvedev said.
"I felt like I didn't break it but I thought maybe one of the ligaments is a little injured so I thought I wasn't going to be able to play.
"That is one of the first times in my life where the physio taped my ankle, so I decided to give it a try and what was very surprising (was that) it was much easier to run than to walk."
Medvedev carried his build up of momentum into the third set, snatching the early break to go up 2-1.
With Medvedev serving for the match at 5-4, 12th seed Zverev secured his second break in 17 chances to extend the contest.
But the German handed Medvedev the advantage right back by double-faulting to gift his opponent another break and a 6-5 lead.
Medvedev did not waste a second opportunity to close out the three-hour, 15-minute contest, taking the game to love when Zverev sent his return wide.
Medvedev said he planned to tape the ankle and take a painkiller to be good to go when he faces Spain's Alejandro Davidovich Fokina in his quarter-final on Wednesday. Fokina beat Chile's Cristian Garin 6-3, 6-4 on Tuesday.
Defending champion Taylor Fritz dug deep into his arsenal to beat Hungarian Marton Fucsovics 6-4, 6-3 to reach the quarters.
Leading 2-0 in the second set, the American closed out a marathon game when he hit a reserve serve - a shot that appears to be going down the tee but is instead directed toward the right-handed opponent's backhand.
The trick shot did just enough to throw the hard-hitting Fucsovics off, as the point and the game ended when the Hungarian sent a forehand out wide.
"I had to kind of just fight through a lot of games," Fritz said.
"I didn't really at times have an answer for it, so I just had to tough it out and get points where I could. I was just able to find a way through."
Fritz next faces either Italy's Jannik Sinner or Swiss veteran Stan Wawrinka.
Elsewhere, 10th-seeded Briton Cameron Norrie upset sixth-seeded Andrey Rublev of Russia 6-2, 6-4 and American Frances Tiafoe was a 6-4, 6-4 winner over Chilean Alejandro Tabilo.