Novak Djokovic was in a crouch, waiting for his opponent’s serve, when he heard a voice yell out from the crowd.

“I love you, Novak!” boomed the woman’s voice during Djokovic’s first-round U.S. Open match at Arthur Ashe Stadium. He stayed in position, but reached one hand behind his back to give a thumbs-up.

The simple gesture summed up Djokovic during this first week at the U.S. Open: Happy in his personal life, clear-headed and focused on the court. An expectant father, the Serbian cruised into the fourth round Saturday with a win over American Sam Querrey, 6-3, 6-2, 6-2.

“I feel just a more fulfilled person in general,” the top-seeded Djokovic said. “I’m so happy and very grateful for the life that I have. So knowing in back of my mind that, you know, now my wife is pregnant and I’m going to become a father, all these things just can give me very positive influence and joy in my life.

“There’s nothing negative and there is no fear or any kind of similar emotion that can get to me.”

Djokovic described his summer as emotionally draining, and his results after winning Wimbledon were disappointing. He lost in the round of 16 at both the Rogers Cup in Toronto and the Western and Southern Open in Cincinnati. From a wrist injury that ailed him during the French Open, where he lost in the final, to winning Wimbledon to getting married shortly afterward, he was mentally checked out.

But bowing out of the tournament early in Cincinnati gave him more time to prepare for the U.S. Open, where he has yet to drop a set. If the whirlwind of the past few months was supposed to deter him from reaching his third straight Grand Slam final, it hasn’t shown in the first week.

Djokovic made Querrey uncomfortable early in their match, returning Querrey’s powerful serve and shaking his confidence in the process. His returns had the 6-foot-6 Querrey running from one end of the court to another. With Djokovic up 5-0 in the first set, Querrey said he started to feel pressure and described the match as a “beatdown.”

“Serves that I hit that are usually an ace sometimes, he’s putting it back in the court with something on it,” Querrey said.

Querrey said it felt like Djokovic was committed to playing good percentage tennis. Djokovic has worked on using his serve more efficiently, going for accuracy and precision over power and speed. He put 69 percent of his first serves in play against Querrey.

Djokovic said he feels like he is peaking at the right time. Although he hasn’t seen his pregnant wife in some time, he video chats with her and said he sees “the stomach is growing.” He thinks there can be a correlation between on-court performance and what’s happening in a player’s personal life, and in his case, everything off the court is ideal.

“Mentally, you’re doing your job and you have that game face on when you’re on the court and when you’re traveling,” Djokovic said. “You want to do your job and win as many matches as you can, but obviously you cannot perform at your best if you have issues in your private life that are taking away, draining your energy. You’re the same person on and off the court, and it’s important to balance everything.”

Djokovic has talked with his coach and other players about balancing fatherhood and a career. Roger Federer, the tournament’s No. 2 seed, started a family while still playing an elite level of tennis. In May, he and his wife welcomed twins, and they also have 5-year-old twin daughters.

“He must be quite excited about what’s going to happen soon,” Federer said. “With the wedding and everything, I’m sure he’s, you know, going through a great spell at the moment with winning Wimbledon, so things are great for him. . . . the good thing, he sees me with four [children], so with one, it should be a piece of cake.”

Djokovic acknowledges his priorities have shifted and tennis is no longer No. 1. But that’s about all that’s changed; his play through the first week of the U.S. Open as good as it’s ever been.

“It would be much wrong if my tennis is in front of my baby and my wife,” Djokovic said. “There is no question about it. You know, my full priorities and commitments and energy goes to my family as much as I need to, but that doesn’t mean that I’m not going to play tournaments or not going to continue doing what I was doing so far.”