SERENA WILLIAMS reached the quarterfinals at Flushing Meadows for a 10th consecutive appearance — she wasn’t there last year because she gave birth to her daughter during the tournament — by picking her level up after a lull and using 18 aces to beat Kaia Kanepi of Estonia 6-0, 4-6, 6-3.

This match was filled with big hitting by both women, along with all manner of shifts in momentum and quality of play. In the 18-minute shutout of the first set, Kanepi’s strokes were off and Williams’ were pretty much perfect as she grabbed 24 of 30 points.

But after compiling 14 winners and only two unforced errors in that set, Williams began making mistakes, becoming less and less comfortable as Kanepi grew increasingly so. Kanepi is ranked only 44th, but she’s been a top-20 player in the past and has made it to Grand Slam quarterfinals a half-dozen times. Sure, that’s nothing compared to Williams’ 23 major titles, but it’s something. Plus, it’s worth remembering this: Kanepi eliminated No. 1 Simona Halep on Day 1 of this tournament.

In a blink, Williams had a match on her hands. Kanepi was matching Williams’ power with booming groundstrokes of her own. She was getting better reads on Williams’ serves. And Williams began making more and more mistakes.

When Williams shanked a backhand return of a 103 mph serve, the match was a little more than an hour old, and it was all tied at a set apiece. That was the first set she had lost against Kanepi of the 10 they’d played to that point, and the first set Williams had lost at the 2018 U.S. Open, a run that included a 6-1, 6-2 victory over her older sister Venus in the third round Friday night.

After a scream-inspiring hold to begin the final set, Williams broke away to lead 2-0. She then faced a break point, but Kanepi wasted that chance by sending a backhand wide.

From there, Williams smacked an ace at 118 mph, followed by a service winner at 113 mph to go up 3-0, and that essentially was that.

Kanepi’s take on Wiliams’ serve? “Unreturnable,” she called it.

Next for the 36-year-old American comes a quarterfinal against 2016 runner-up Karolina Pliskova, who beat Williams in the U.S. Open semifinals that year. (SD-Agencies)