Norrie, who snapped a six-match losing streak en route to the semi-finals in Los Cabos last week, followed up his opening win in Canada over Camilo Ugo Carabelli with more success against Peruvian Ignacio Buse 6-3 6-3.
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Speaking on Sky Sports Tennis, analyst Annabel Croft said: "Norrie was too experienced, too much game for his opponent. He applied the pressure when he needed to and defended extremely well with depth. We also saw him coming forward a lot, asking a lot of questions.
"His serve went a little off in the second set but he got it back on track."
Buse vs Norrie: Tale of the Tape
Fonseca makes winning return
Competing in his first tour-level match since Wimbledon, Fonseca overcame former finalist Stefanos Tsitsipas 7-6 (7-3) 7-5.
"I think Joao from last year would've lost his mind," Fonseca said in his on-court interview.
"I'm a more mature Joao [now]. It's been a couple weeks without playing, so I knew, serving for the match, I would be a little bit more tense.
"I felt good, played some good returns, and then put the pressure on him. I think I needed that break at 5-5."
The Brazilian wonderkid added: "This year, playing with the big [guys]. I've played with Sinner, Alcaraz, Zverev, Shelton and Djokovic, so I've had a lot of experience.
"This has helped me a lot figuring out how much my mental strength is one of my biggest weapons. That I can be as confident as this.
"These experiences that I've had in these two years [has been] really important for my development."
Home favourite Ben Shelton starts his title defence with 6-3 7-5 win over Jenson Brooksby, while Casper Ruud - sporting a new haircut - crushed Juan Manuel Cerundolo 6-1 6-2.
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