The ankle couldn’t stop her. The top-20 foe couldn’t even slow her. And with each rout, it looks more and more like Serena Williams is destined to win this U.S. Open. And take her place in history.

Williams was confident this tourney was hers to lose, even before the top four seeds went by the wayside. But if she keeps playing the way she did in a 6-1, 6-0 quarterfinal blitz of Qiang Wang, it’s hard to see anybody coming between her and a milestone title.

Such is the zone Williams finds herself in.

“It feels good,” she said. “It feels like, ‘OK, this is what I’ve been training for; this is how hard I’ve been working.’ It feels like hard work pays off when that happens.”

Williams made short work of Wang, despite having rolled her right ankle in her round of 16 match two days earlier. Her 44-minute clinic was the quickest of this Open, and arguably its most dominant.

No. 18 Wang — whose coach, Peter McNamara, died of cancer on July 20 — didn’t notch a winner the entire match. Williams had 25 to just 10 unforced errors.

Williams dominated the first five games, and after losing the sixth when her lob sailed just long, she ran off the next 11 straight points. She clinched the first set at love, opened the second set at love and cruised the rest of the way.

And she did it all while moving well. She got had right ankle retaped in the second set, but covered the court as well as she has in a while in her most lopsided win since Madrid four years ago.

“I’ve been working on my speed, getting shots. I didn’t give her too many chances in the match,” Williams said of not conceding a single winner.

“Yeah, that’s a good stat for me. It’s good because I want to be able to move around the court. I move when I want to move; I guess I wanted to move.

“Less errors are always good. It’s actually yet another thing I’ve been working on. Hopefully things will start coming together one of these days.”

Self-deprecation aside, Williams improved to 100-12 at the U.S. Open, one win shy of Chris Evert’s mark. And beating Elina Svitolina in Thursday’s semifinal would give her a shot at an even bigger record — Margaret Court’s 24 Grand Slam singles crowns.

Williams has been one title shy of the record since giving birth to daughter Olympia two years ago. Since motherhood, she’s 32-5 in Grand Slam play with three finals berths; but she lost all three, including last year’s testy defeat here in Flushing Meadows.

“I’m definitely more ready than last year, though I thought I was playing well,’’ Williams said on ESPN. “I’ve learned in the last several Grand Slam finals that I have to be ready; I can’t underestimate [anyone].”

Least of all Svitolina, against whom she’s 4-1, but Williams lost to her in the 2016 Rio Olympics.