Rafael Nadal battled past big-hitting American Reilly Opelka 7-6 (7/3), 7-6 (7/5) on Wednesday to push his 2022 record to 18-0 and reach the quarter-finals of the Indian Wells WTA and ATP Masters.

The 35-year-old Spaniard, who won a record-setting 21st Grand Slam title at the Australian Open in January and lifted the trophy in Acapulco last month, stayed on track for a fourth title in the California desert.

But he had all he could handle from the 2.11m tall American, including a raft of serves that topped the 140 mph mark and had Nadal's back against the wall -- literally.

"I manage it so-so," he said of Opelka's serve, which the Spaniard stood as far back in the court as possible to receive. "I don't know if the cameras can follow me like 10 meters behind the baseline.

"It's difficult because it's not only about the speed," Nadal added. "It's difficult to read his serve because the serve is coming sometimes with topspin, sometimes slice.

"At the same time it's not enough just to put the ball in because then he has a huge forehand.

"So it's a great victory for me against one of the toughest opponents that I can play," said Nadal, who called it his best performance of the tournament so far.

It was a tense affair from the outset, Opelka saving the only break point of the opening set.

A patient Nadal worked the rallies in the tiebreaker and after he gained a 4-3 lead Opelka produced three straight errors to surrender the set.

Impervious on his own serve in the opening set, Nadal gave Opelka a break chance with a double fault in the fifth game of the second and the American pounced on it.

Unable to take advantage of a break point in the next game, Nadal saved three more break points in the seventh game before breaking back to knot it at 4-4.

Nadal roared ahead in the second set tiebreaker, and after Opelka saved two match points with thundering serves the Spaniard finished it off with a winner.

Nadal became just the second player to start a season 18-0 since the ATP Tour launched in 1990. Novak Djokovic has done it twice, starting 41-0 in 2011 and 26-0 in 2020.

Berrettini bounced

In other matches, Serbia's 61st-ranked Miomir Kecmanovic shocked sixth-ranked Matteo Berrettini 6-3, 6-7 (5/7), 6-4 to book a quarter-final clash with American Taylor Fritz.

The 22-year-old Kecmanovic equalled the biggest win of his career as he reached the last eight of a Masters level event for the second time.

Berrettini, runner-up at Wimbledon in 2021, is at a career-high sixth in the world after reaching the Australian Open semi-finals in January.

But he couldn't find the answer against an aggressive Kecmanovic, who pressured Berrettini's serve throughout.

Unable to convert two break points in the eighth game of the final set, Kecmanovic broke Berrettini to love in the final game, letting out a shout of triumph as the Italian sent a forehand wide on match point.

Kecmanovic will now be hoping to go further than his quarter-final run in the California desert in 2019.

Standing in his way will be 20th-seeded American Fritz, who shook off a slow start to beat Australian Alex de Minaur 3-6, 6-4, 7-6 (7/5).

Women's quarter-final action got underway on Wednesday, with third-seeded Iga Swiatek of Poland taking on American Madison Keys and former world number one Simona Halep facing Petra Martic.

Swiatek, 20, is coming off a title in Doha last month, has rallied from a set down in each of her matches this week, including an impressive fourth-round comeback against German world number one Angelique Kerber in which Swiatek trailed by a break in the final set.

Romania's Halep, a two-time Grand Slam champion who lifted the Indian Wells trophy in 2015, will be facing Martic for the first time since she beat the Croatian in the quarter-finals here in 2018.