Teenage seventh seed Carlos Alcaraz fought back from a poor set to win 2-6 6-2 6-1 over fellow Spaniard Jaume Munar at the Rio Open on Monday.
The 18-year-old struggled for rhythm in the opening set but showed composure to respond by breaking Munar early in the second set and dominating from there.
Alcaraz took the victory in two hours and 15 minutes, saving 10 of 13 break points across the match, while dropping only three games in the second and third sets.
Spaniard Pedro Martinez set up a second-round clash with third seed Diego Schwartzman after a 6-3 6-4 win over Shang Juncheng.
Pablo Andujar Alba also progressed 7-6 (7-2) 7-5 over Pablo Cuevas, while Serbian qualifier Meomir Kecmanovic accounted for local wildcard Felipe Meligeni Rodrigues Alves 6-3 6-0.
At the Delray Beach Open in Florida, Steve Johnson beat South African veteran Kevin Anderson in just over two hours, triumphing 6-2 6-7 (5-7) 6-2.
Oscar Otte got past Yoshihito Nishioka 7-6 (10-8) 6-3 to set up a second-round date with top seed Cameron Norrie, while there were only two breaks across the match as seventh seed Maxime Bressy was ousted by John Millman 6-7 (2-7) 7-6 (7-2) 7-6 (7-3).
Italian veteran Andreas Seppi beat German Peter Gojowczyk 7-5 6-4, while young American Brandon Nakashima comfortably handled Denis Kudla 6-1 6-1.