The 22-year-old Spaniard used an early break in each set and saved all three break points he faced in a confident performance at Hard Rock Stadium, where 19-year-old Fonseca was cheered by a raucous contingent of fans on Friday.
“I was really good from the beginning until the last ball,” Alcaraz said. “I know how good Joao is and that’s why I was really focused, every point, every shot, trying to figure out what is the best possible shot for me.”
Alcaraz bounced back from his semi-final loss to Daniil Medvedev at Indian Wells last week to improve to 17-1 in 2026.
That includes an Australian Open title that made him the youngest man to complete a career Grand Slam and a title in Doha.
“He had a lot of chances to stay in the match to [keep it] tight, so I’m just happy to stay calm, stay positive at these moments,” said Alcaraz, who next faces American Sebastian Korda, a 6-0, 6-3 winner over Camilo Ugo.
Women’s number one Aryna Sabalenka held off determined American Ann Li 7-6 (7/5), 6-4 to launch her Miami title defence.
The Belarusian was pleased to get through in straight sets against her 39th-ranked foe in a match moved to the third show court as organizers hustled to get the rain-hit tournament back on schedule.
“I was there, I was fighting no matter what, even though my game probably wasn’t the best one that I have,” Sabalenka said.
Fourth-seeded American Coco Gauff and sixth-seeded compatriot Amanda Anisimova also reached the third round.
French Open champion Gauff rallied to beat Elisabetta Cocciaretto 3-6, 6-4, 6-3 in a match delayed several hours by rain while Anisimova outlasted Australian veteran Ajla Tomljanovic 6-1, 5-7, 6-4.
In other men’s action, 56th-ranked American Ethan Quinn upset Norway’s 11th-seeded Casper Ruud 6-4, 7-6 (9/7), saving seven set points in the second set on the way to victory.
Japanese wildcard Rei Sakamoto bagged his maiden ATP match win, converting his fifth match point in a 6-4, 3-6, 7-6 (9/7) first-round victory over Aleksandar Kovacevic.
The 19-year-old ranked 164th booked a showdown with in-form Indian Wells finalist Medvedev. (AFP)
Edited by Robert Kemp
