Defending champion Carlos Alcaraz avoided the prospect of an early US Open exit by fighting back from a set down against Portugal's Jaime Faria.
Alcaraz, 23, needed time to find his rhythm in the second-round contest as he continues to make his comeback from a long-term wrist injury.
But the Spanish second seed asserted his authority to win 4-6 6-0 6-3 6-2 against world number 72 Faria in the New York night session.
Alcaraz fighting off two break points in the first game of the second set proved to be pivotal.
"It was a tough match for me. I felt great in the first set, but I didn't take time and that cost me," said the seven-time Grand Slam champion.
"After that I tried to be focused, stay calm and think the good things will happen."
Going into the final major of the season, everyone wondered how Alcaraz would fare in his first tournament since mid-April following an injury to his playing right wrist.
The latest evidence showed the two-time US Open winner is beginning to gather momentum.
Alcaraz said he was playing "normal" in a straight-set win over Russia's Roman Safiullin in the first round and reiterated after beating Faria that he is not holding back on his forehand.
"I know once I step on the court, I've just got to go for it every time. I've got to feel normal," said Alcaraz.
"I have to hit like I was hitting before the injury. I'm feeling great. There is no reason to be afraid and not hitting normal."
After coming through his opening match with little fuss, the questions then turned to how Alcaraz would pull up physically two days later.
Sweeping aside 23-year-old Faria answered those emphatically, although Alcaraz knows the tests will get tougher if he is able to move further through the draw.
As well as the likelihood of facing opponents ranked much higher than Safiullin and Faria, it will be interesting to see how his body continues to react to playing more five-set matches in quick succession after such a long absence.
On whether he wished he had been quicker against Faria, Alcaraz said: "At the end, I realised that playing four sets was really good for me to test everything physically, to test my body, how I feel, and how I'm going to feel tomorrow after this match."
With his fierce rival Jannik Sinner missing from New York through injury, and 24-time major champion Novak Djokovic already out, Alcaraz might increasingly fancy his chances of going all the way in a draw which looks to be wide open.
Alcaraz's next challenge will be overcoming China's Wu Yibing, who is ranked 113th in the world, in the last 32.
Meanwhile, American 20th seed Tommy Paul - a potential opponent for Alcaraz in the fourth round - continued his progress with a 6-2 6-3 5-7 6-4 victory over Croatia's Dino Prizmic.
Paul goes on to face Kazakh 15th seed Alexander Bublik, who cruised past French veteran Adrian Mannarino in a 6-3 6-1 6-1 win.
Eighth seed Ben Shelton continued his own quest to become the first American men's champion since Andy Roddick in 2003 with a 6-3 5-7 7-6 (7-3) 7-5 victory over Poland's Hubert Hurkacz.
Two-time semi-finalist Frances Tiafoe, another home favourite, demonstrated his great form with a 6-3 7-6 (7-2) 7-5 win against Japan's Rei Sakamoto, while Argentina’s Mariano Navone backed up his stunning first-round knockout of Djokovic with a 3-6 6-3 6-4 7-6 (7-4) victory over 2021 Wimbledon runner-up Matteo Berrettini.
Spanish 12th seed Rafael Jodar was the biggest casualty in the men's draw on day four as he was beaten 6-2 6-1 6-1 by Chinese world number 124 Bu Yunchaokete.
