Alexander Zverev of Germany won the gold medal in the Olympic tennis tournament Sunday, defeating Karen Khachanov of Russia in straight sets 6-3, 6-1.

The tournament victory was arguably the most significant of Zverev’s career, especially considering he upset Novak Djokovic, the world No. 1, in the semifinal. Djokovic, the winner of the year’s first three Grand Slam tournaments, was seeking a Golden Slam and needed the Olympic gold medal and the U.S. Open title later this summer to achieve it.

Zverev called the win over Djokovic the proudest moment of his career, but he did himself one better Sunday in beating Khachanov, 25, a powerful Russian whose game lately has shown signs of the promise that characterized his first years on the tour.

But midway through the second set against Djokovic, Zverev experienced a revelation — that he needed to stop rallying and start swinging through the ball. He reeled of 10 of 11 games to send Djokovic packing and picked up Sunday right where he left off.

Zverev broke Khachanov’s serve in the third game of the first set then once more in the ninth game to take the first set, forcing Khachanov into a sloppy volley that sailed wide of the open court.

Zverev never looked back from there, bullying Khachanov with big serves and searing backhands and even sprinkling in the occasional drop shot and topspin lob.

A huge soccer fan, Zverev played in a white shirt with black trim on the sleeves — and a hint of tennis ball yellow — that was awfully similar to the uniform that Germany’s six-time World Cup champion soccer teams wear.

He looked every bit the worldbeater Sunday against Khachanov. By the middle of the second set, Khachanov had lost the zip in his legs. Down 0-5 and in danger of an embarrassing end, he whacked a ball high into the empty stadium seats.

How different a player Zverev seems now from 11 months ago when, in the late stages of the U.S. Open final, his game devolved into a series of slices and soft second serves.

Zverev blasted a 130 m.p.h. ace to get to within two points of the gold medal, pushed perfect backhand volley for match point then clinched the gold medal with a blast off his forehand from the middle of the court. When Khachanov’s last swing sent the ball into the bottom of the net, he collapsed to his knees and buried his face on the pavement.