Novak Djokovic celebrates after his win. (Carlo Allegri/Reuters)

Playing on the undercard after the Williams sisters’ primetime match Tuesday night, No. 1 Novak Djokovic did what Djokovic does: hitting 36 winners to 17 unforced errors while beating No. 18 Feliciano Lopez, 6-1, 3-6, 6-3, 7-6 (7-2).

The win, which came at 1:07 a.m. in New York, earns Djokovic a spot in a Grand Slam semifinal for the seventh straight time and the 21st time in the past 22 major events. He has now made nine straight U.S. Open semis.

Lopez, the 33-year-old Spanish lefty playing in his first U.S. Open quarterfinal, had a chance to push Djokovic to the No. 1 seed’s fourth five-set match of 2015 when the fourth set went to a tiebreak. Lopez won the first set in that race to seven, but Djokovic responded by winning six straight points.

Earlier in the match, Lopez had Djokovic yelling from his seat after dropping the second set.

But the 28-year-old Serbian responded by winning the first three points of Lopez’s first service game in the third set and eventually clinching the break on a double fault from Lopez. That would be the last break for either player.

“It was a pretty good match,” Djokovic said. “Obviously it was frustrating at times, but this is the quarterfinals at a Grand Slam. This is what you expect.”

Cilic staves off Tsonga

Marin Cilic steamrolled his way to his first Grand Slam title at last year’s U.S. Open, winning his final 10 sets.

He was on the path toward another late-tournament straight-set victory in Tuesday’s quarterfinals, winning the first two sets against No. 18 Jo-Wilfried Tsonga. Then Tsonga had other ideas.

Even as he dealt with a knee injury, Tsonga managed to claim the third set and then win a fourth-set tiebreaker, saving three match points along the way.

The defending champion was undaunted, however, and rebounded to advance with a 6-4, 6-4, 3-6, 6-7 (7-3), 6-4 victory. The No. 9 seed needed five match points before getting the clincher, at which point he turned to the stands and held his arms in the air, 3 hours and 59 minutes after the match started.

The win extended Cilic’s undefeated mark when winning the first two sets of the match to 48-0.

“A big mental fight,” Cilic said, “Especially after losing that fourth set and having I guess three match points, and on all of those I played pretty well and Jo just came up with amazing shots.”

Cilic got the game-altering break he needed in the fifth game of the fifth set, winning all four points in that game as Tsonga double-faulted and hit two unforced errors. In total, Cilic was 3 for 14 in break-point opportunities while Tsonga was 1 for 10.

One of those 10 break points came in the match’s final game as Tsonga earned an advantage by forcing a Cilic error, but the Croatian recovered on the next point, attacking the net and hitting a backhand volley winner before winning the match’s final two points at the baseline.

“He just hit the ball a little bit more properly than me at the right moment, and that was a huge difference at the end,” Tsonga said.

Vinci advances

The quarterfinal match between Kristina Mladenovic and Roberta Vinci was about as close as you’d expect a faceoff of the world’s No. 40 and No. 43 players to be, as they split the first two sets. Then it got even closer.

With the deciding set tied at 3, the 22-year-old Mladenovic and 32-year-old Vinci battled for more than 15 minutes during one Mladenovic service game.

Coming into the match, neither player had reached the semifinals of a Grand Slam event. Mladenovic, who was once the top junior player in the world, was looking to build on her best year as a pro, while Vinci, a five-time Grand Slam champion in doubles, sought a late-career breakthrough.

As the afternoon shade nearly enveloped the court, Mladenovic double-faulted twice to give Vinci her fifth break point of the game after the two played 10 deuce points. Vinci took advantage, forcing a Mladenovic error with a tricky short ball.

Vinci raised a fist in triumph at the end of the game, while Mladenovic dropped the ball she was holding, went to her chair and leaned her head back to exhale while a trainer came over to work on her upper left leg.

Vinci won her next two service games, throwing both of her fists in the air when she clinched the 6-3, 5-7, 6-4 win.

Vinci had not played since Friday, moving into the quarterfinals when No. 25 Eugenie Bouchard withdrew after suffering a concussion off the court, and still has not been matched against a seeded opponent.

Mladenovic, meanwhile, upset No. 13 Ekaterina Makarova late Sunday night and then lost in a two-hour doubles match Monday.

Combine those long matches with what Mladenovic described to be the hottest conditions she’s faced yet and the nerves of her first ever Grand Slam quarterfinal, and her struggles make sense, she said after the match.

“I was wondering how I will handle everything,” Mladenovic said. “I just gave it all out there. I really tried to fight till the very last second I could.”