Alexander Zverev won his 16th successive match, but were the signs all good for his potential US Open semifinal with Djokovic?

FLASHBACK: Zverev's match point vs. Harris in Cincinnati

Looking at the scores, Alexander Zverev’s 7-6 (6), 6-3, 6-4 win over Lloyd Harris appears to be exactly the type of one-sided affair that we would expect from a player who had won his last 15 matches. It also looks like the type of match that anyone hoping to challenge Novak Djokovic and/or win his first Grand Slam title would be pleased to have played.

Numbers-wise, Zverev should be happy. He hit 21 aces. He made 43 winners and just 26 errors. He was 12 of 15 at the net. He won 82 percent of his first-serve points. He’s lost just one set in five matches in New York. Now he gets to sit back and watch Djokovic and Matteo Berrettini battle for the right to play him in the semifinals.

In other ways that don’t show up in the stats, though, this match may have been worrying for Zverev. Harris served for the first set, and served again at 6-5 in the tiebreaker. Up to that point, he had been the better player. Just before that 6-5 point, though, Zverev asked for the scoreboard above the court to be turned off, because it was distracting him. The delay was enough to cause Harris to completely implode. He put a forehand into the net to make it 6-6, shanked another to make it 6-7, and missed a return to give Zverev the set.

Enraged on the changeover, Harris chucked two water bottles onto the court in front of his chair. When they exploded and soaked the surface, he, Zverev, and chair umpire Louise Engzell joined the ball kids in drying it off.

Life didn’t get much better for Harris after that. He kept missing forehands, and kept losing his serve. Yet despite having the lead, Zverev was hardly a picture of calm confidence. Serving at 5-3 in the second set, he tightened up badly, went down 0-30, and threw in a 79-m.p.h. second serve. The ghosts of last year’s Open final, and his inability to close it out from two sets up, seemed to be haunting him. Again, Harris came to the rescue. Seeing Zverev get nervous seemed to make him nervous as well. He slugged two routine forehands into the net, and Zverev escaped again.

“I think the match was a little bit strange,” Zverev admitted. “I think the first set he played very well, didn’t give me a lot of chances on his serve. Yeah, I mean, after that I started to play much better.”

“I think the turning point was the first set … I won it, and it did kind of go my way after that.”

Zverev went up 4-0, in the third, but he still wasn’t out of the woods. He continued to be irritable, throwing his racquet to the court and complaining to his player box. He ended up almost talking himself out of the set. When Harris broke serve, Zverev tightened again. Serving at 4-2, deuce, he decided to gun a second serve rather than risk choking on a normal second delivery. The result was a 129-m.p.h. ace that effectively ended the match.

In the commentator’s booth, Jimmy Arias talked about Zverev’s psychology, which is unusually up-and-down for a top player, especially one on a 15-match win streak.

“When he’s confident, he’s kind of unbeatable,” Arias said of the No. 4 seed. “but there are moments when he can feel tension.”

Everyone feels tension, of course, but Zverev is affected by it in obvious ways. He decelerates on his second serve, as well as on his forehand, and he did both when he had to close out the last two sets today.

If Zverev does play Djokovic on Friday, and he builds an early lead, will his serve-and-forehand woes reappear? Or will he feel like he has nothing to lose because he’s playing the world No. 1, and he’ll keep swinging freely?

All of that remains in the future. For now, Zverev is right where he wants to be, in the semifinals at the Open, with a chance for much more.