Defending champion Carlos Alcaraz got pushed in his second-round match at the 2023 U.S. Open.

And though he took his foot off the gas, he had a big enough lead to win this race, a 6-3, 6-1, 7-6 (4) victory over Lloyd Harris on Thursday.

After his opponent, Dominik Kopefer, retired in their first-round match, Alcaraz faced a feisty foe at Arthur Ashe Stadium, and Harris hit him with a powerful array of shots.

But Alcaraz had all the answers when he needed them.

“Yeah, I think I played a great match. But obviously in the third set he started to play better,” Alcaraz said. “I got down a little bit. I needed extra energy in the third set.

“That’s normal. In a Grand Slam, matches are much longer. You need that extra energy that I need in the third set. In the end, I think I play a pretty good match and I try to keep the same level into the next round.”

At just 20 years old, Alcaraz is the youngest top seed in U.S. Open history and is being hailed as the future of the sport.

Alcaraz’s first two sets were the kind of tennis he’ll have to play if he plans to beat Novak Djokovic — and become the first man to repeat at Flushing Meadows since Roger Federer in 2008.

That third set will need tightening up.

Alcaraz showed his great forehand and impregnable defense. His serve wasn’t as crisp late, and South African Harris played beyond his No. 177 world ranking, making some great shots and big second serves that earned him an ovation from the crowd as he walked off the court.

Just two years ago, Harris reached the Open quarterfinals and was ranked 31st in the world.

But he missed the final six months of last season with a wrist injury, and flashed signs of his talent late in the match against Alcaraz.

Harris served well and played big with 26 winners, but Alcaraz showed off his defense with great gets.

Alcaraz played with his customary joy, even high-fiving Harris after impressive points that the Spaniard lost.

Down a break in the third set against a strong server, Alcaraz broke Harris and then won a tiebreaker to close it out in three sets.

“Well, I’m really, really happy to be able to win that match in straight sets,” Alcaraz said. “I was break down in the third set. Be able in the next set break again, it was really helpful for me to stay there and to stay strong mentally. I try to forget that game and was really focused on the next one, the return one.

“I did pretty good returns in that game that I had the chance to be up in that game, try to put my game, try to be aggressive, go to the net. It was really good for me to break and have the chance to push me up a little bit and be able to play a great level at the end.”