MIAMI (AFP) — Jannik Sinner powered into the Miami Open quarterfinals on Tuesday, defeating unseeded American Alex Michelsen in straight sets to stay on course for the “Sunshine Double.”

The Italian second seed Sinner, who is bidding to follow up his triumph at Indian Wells with victory in Miami, bided his time before completing a 7-5, 7-6 (7/4) win in one hour and 41 minutes.

The four-time Grand Slam champion, who will face 19th seed Frances Tiafoe in the quarterfinals, was made to work hard by the 40th-ranked Michelsen.

After a cagey opening Sinner began to put pressure on Michelsen’s serve in the ninth game of the first set, carving out three break points.

Michelsen rode out that storm, but Sinner finally broke through in the 11th game before serving out for the first set.

Michelsen hit back in the second set, breaking Sinner for a 4-2 lead before holding to go 5-2 up.

Michelsen appeared to struggle with the bright late afternoon sunlight on the Hard Rock Stadium’s main court and Sinner came roaring back to force a tiebreak.

Sinner sealed the win with a thumping serve that Michelsen could only return wide.

“I feel like I served very well in important moments and that helped me out, especially in the tough moments,” said Sinner, who unfurled 15 aces to Michelsen’s three.

“But today was not easy — I played a night match yesterday and today in the daytime, so the conditions were very different.”

Home hope Tiafoe advanced to his quarterfinal date with Sinner after battling past France’s Terence Atmane 6-4, 1-6, 6-4.

Spanish qualifier Martin Landaluce, ranked 151st in the world, upset American 32nd seed Sebastian Korda to score a 2-6, 7-6 (8/6), 6-4 victory.

The win marked another impressive victory for the 20-year-old Landaluce, who eliminated Russian 14th seed Karen Khachanov.

Korda, who had beaten world number one Carlos Alcaraz in the previous round, had a match point late in the second set, but Landaluce survived to set up a quarterfinal against Czech 21st seed Jiri Lehecka.

Landaluce, who had failed to register a single win at tour level in 2026 before arriving in Miami, dedicated his latest success to his late grandmother.

“She would have been 101 last week, and she passed away a few months ago. I wanted to give her the victory,” Landaluce said.

Lehecka booked his place in the quarterfinals by ousting sixth seed Taylor Fritz 6-4, 6-7 (4/7), 6-2 in two hours and 25 minutes.

“I just felt that in the third set, if I wanted to beat a guy like Taylor, I just needed to go for it and be aggressive,” Lehecka said.

American 22nd seed Tommy Paul set up a quarterfinal against France’s Arthur Fils after cruising past Argentina’s Tomas Etcheverry 6-1, 6-3.

Fils beat Monaco’s Valentin Vacherot 6-4, 6-7 (4/7), 6-4.

Argentina’s 18th-seeded Francisco Cerundolo followed up his upset of Daniil Medvedev on Monday with a comfortable 6-4, 6-3 defeat of French 31st seed Ugo Humbert.

Cerundolo will face Alexander Zverev in the last eight after the German third seed defeated France’s Quentin Halys 7-6 (7/4), 7-6 (7/1).