Novak Djokovic’s barking left shoulder took a 180 degree turn. A heckler he confronted during his pre-match practice session fired him up.

Combine those two factors, and American Denis Kudla didn’t have a chance against the top-seeded Serbian, as Djokovic looked every bit the world-class superstar who has already won the Australian Open and Wimbledon this year.

“I’m very glad with the way it went. I am able to play,” said Djokovic, who didn’t practice the day before the match to rest his ailing shoulder. “That for me is a huge blessing because it was probably the complete opposite [of] two days ago.”

Djokovic needed just over two hours to breeze past Kudla in straight sets, 6-3, 6-4, 6-2, on Friday night at Arthur Ashe Stadium, showing no signs of being compromised by a sore left shoulder that had been bothering him.

Before the match, Djokovic engaged a fan. A video captured the 16-time Grand Slam champion confronting and pointing at the fan.

“I’ll come find you,” he told the fan. “Trust me, I’ll come find you.”

Djokovic didn’t deny the comments were made and joked it was about meeting up with the fan to have a drink. He didn’t reveal what was said to him that led to the confrontation, other than to say the heckler had a few too many drinks.

“I think he did me a favor,” said Djokovic, who will meet 23rd-seeded Stan Wawrinka, who defeated him in the 2016 U.S. Open final, in the fourth round. “Even maybe he didn’t want to do me a favor, he did me a favor — big favor.”

Djokovic, the defending U.S. Open champion who hasn’t dropped a set in three matches here, was bothered by his shoulder in the second round on Wednesday, twice being attended to by a trainer. After the previous victory, he said he had been playing with pain and was “lucky.”

Luck wasn’t involved in his latest victory.

Djokovic toyed with Kudla, showcasing his world-class game. He overwhelmed Kudla from the baseline, didn’t lose his serve a single time, though he did have to fight off seven break points, and won 15-of-20 points at the net.

As for his shoulder, Djokovic wouldn’t reveal the diagnosis. He did a lot of things to be able to play, but isn’t sure if he will continue resting the day before his matches.

“It’s almost pain-free,” he said. “[It] has a little bit of pain, but I’m really pleased with the way it went.”