In routing Marin Cilic, Jack Sock got the holiday weekend started with a U.S. Open BBQ

NEW YORK—Arthur Ashe Stadium plays host to the stars. The new Grandstand has generated the buzz and the headlines. But on Friday, as it filled up with fans who seemed determined to get a jump on the Labor Day weekend, Louis Armstrong Stadium put on a party. The only thing missing from the all-American atmosphere was a BBQ pit in the stands.

Nebraska native Jack Sock walked on court wearing the traditional garb of the U.S. male tennis player: a backwards baseball cap. Soon a group of fans dressed in red-white-and-blue began to bellow—can you guess?—“USA! USA! USA!” The Wave started in an upper corner of the arena. Another set of spectators chanted “Jack! Jack! Jack!” Over the PA system, the Rolling Stones’ “Get Off My Cloud” blared like a warning. A voice from far up in the bleachers rose above the din: “Bury this guy, Jack!”

It was Davis Cup, Queens-style.

Sock’s opponent, Marin Cilic of Croatia, must have felt as if he had walked into a lion’s den rather than onto a tennis court. That’s how he played, too—like a man who knows his fate before the contest has begun. In July, Cilic helped Croatia beat the U.S. in the (real) Davis Cup quarterfinals in Portland. In August, he played some of the best tennis of his career to win his first Masters title, at the Western & Southern Open in Ohio. That victory made him a consensus dark horse at the Open.

Today, though, it looked as if Cilic had left his heart, and his game, in Cincinnati. Unable to mount any sort of attack or gain traction on his own serve, Cilic watched helplessly as Sock stormed past him with dumbfounding ease, 6-4, 6-3, 6-3, in one hour and 41 minutes. The American never faced a break point.

“Today big for me was the variety,” Sock said. “A lot of kick serves trying to get out of the strike zone and keep him on the move and throw in some slice. Was able to work well, especially in the windy conditions.”

Sock’s topspin allowed him to handle the wind better than Cilic, and his serve and forehand backed the Croat up and took the racquet out of his hands. Cilic made 21 unforced errors, but Sock forced him into 41 more. Cilic drove his returns into the bottom of the net and shanked his forehands high into the sky. At one point, Cilic had his thighs rubbed by the trainer, and he looked slow to track down a drop shot, so he may not have been in peak condition. More important, though, was the fact that any time he threatened to get his foot in the door, Sock slammed it in his face.

At 23, the American is into the fourth round at the U.S. Open for the first time. Today he looked like a player who is discovering that his talent athleticism could take him farther than he ever allowed himself to believe before. Sock says a renewed focus on singles (he stopped playing doubles with Vasek Pospisil this summer), and an improved return have raised his expectations.

“Maybe in years past, maybe I was...happy to make the third round and, you know, kind of whatever happens happens,” Sock said today. “But I feel like definitely more on a mission this year.”

Sock has always had the explosiveness; his arm speed and foot speed are among the best on tour. But often he has seemed to lose something in the middle of a match, whether it be concentration, fitness or belief. In his first-rounder against Taylor Fritz, the match followed Sock’s mood over the course of its five topsy-turvy sets. But that wasn’t the case against Cilic; Sock didn’t waste a shot today. Even against a player in the Top 10, it was obvious that the rallies resided on the 27th-ranked American’s racquet. This time the chatty Sock let his athleticism do the talking, and his opponent had no answer.

Finally, in victory, Sock joined the party; he celebrated by jabbing his racquet toward his player box, in a tribute to Miles Chamley-Watson, a U.S. fencer who Sock befriended at the Olympics, and who was in the crowd today. Sock won a gold medal in mixed doubles in Rio, and he told the Armstrong crowd that he loves to “put it on the line” for the fans in the States.

What else can Sock—a man who ran for president this year in an ad campaign for his racquet company—do with his country behind him?