Daniil Medvedev kept alive his bid for a fourth successive title after overcoming a "tricky" third-round battle with Ilya Ivashka at the Indian Wells Masters on Sunday.
Medvedev, seeded fifth, extended his winning run to 16 matches with a 6-2, 3-6, 6-1 victory over 85th-ranked Ivashka and will face German 12th seed Alexander Zverev for a place in the quarter-finals.
"Always tricky to play here," said Medvedev, who arrived in California following a hat-trick of titles at the Rotterdam Open, Qatar Open, and Dubai Duty Free Tennis Championships.
"(It's) tough to make anything during the rallies, so just have to kind of see who puts more balls in court. If you lose a little momentum you lose a set."
Medvedev was clearly frustrated at the end of the second set, grumbling to the referee that he would be "as slow as the court" in taking a bathroom break.
The Russian former world No 1 managed to pull himself together, though, to take a 5-0 lead in the third. Serving to prolong the match, Ivashka went down 0-40, but reeled off three straight points and held serve with an ace to force Medvedev to serve it out.
"I missed less. That's the only thing you can do. You cannot do more," Medvedev, 27, said. "It was a matter of a few points.
"Second and third sets for me they were kind of the same, the score is completely different. It's just who plays better the most important points -- break points, 30-all. I managed to do better in the third set."
Medvedev's fourth-round opponent, Olympic champion Zverev, said he felt fortunate to come out with a 7-5, 1-6, 7-5 victory over Finland's Emil Ruusuvuori, whom he judged "the much better player" in the third set.
The shock of the day saw qualifier Cristian Garin defeat third-seeded Casper Ruud 6-4, 7-6 to reach the fourth round while Cameron Norrie survived a scare.
Garin's attacking game paid off as the 97th-ranked Chilean dispatched world number four Ruud in just under two hours.
"The way I played today I'm so happy," Garin, 26, said. "I was aggressive the whole match."
His 39 winners were too much for Ruud, a two-time Grand Slam finalist last year who had hoped a quick victory over Diego Schwartzman in his second-round opener would mark a turnaround in a season where he hadn't advanced past the second round in three prior tournaments.
Tenth-seeded Norrie, who reached the final in Buenos Aires and lifted the trophy in Rio de Janeiro last month, was down a set and 4-1 to Japanese qualifier Taro Daniel before rallying for a 6-7, 7-5, 6-2 victory.
Another Chilean qualifier joined Garin in the fourth round as Alejandro Tabilo triumphed 6-3, 7-6 over unseeded Jordan Thompson, who had upset second seed Stefanos Tsitsipas in the second round.
Tabilo lined up a meeting with American Frances Tiafoe, who eased past Aussie Jason Kubler 6-3, 6-2.
Sabalenka receives walkover as Pegula battles through
On the women's side of the combined WTA and ATP Masters 1000 event, second-seeded Australian Open champion Aryna Sabalenka of Belarus advanced by walkover when Ukrainian qualifier Lesia Tsurenko withdrew from their scheduled match.
Tsurenko has now lost by retirement or walkover in nine of her 18 tournaments dating back to Indian Wells last year.
Third-seeded American Jessica Pegula again rallied from a set down, beating Anastasia Potapova 3-6, 6-4, 7-5.
"That was definitely a battle today," said Pegula, who also rallied from a set down in her second-round win over Camila Giorgi. "She definitely came out hitting her shots and painting lines and going after it.
"So I'm just glad I was able to work my way back into the match and ended up playing much better than how I started."
Sixth-seeded American Coco Gauff advanced with a brisk 6-4, 6-3 victory over Linda Noskova.
But last year's runner-up, Maria Sakkari, needed two-and-a-half hours to seal a 3-6, 6-2, 6-4 win over Anhelina Kalinina – Sakkari's second straight come-from-behind victory.