Even as Serena Williams piled up aces and groundstroke winners from all angles, even as she stormed through seven games in a row and 10 of the last 13 in yet another comeback, her Wimbledon quarterfinal against Victoria Azarenka never felt like a runaway.

That’s because Azarenka, a two-time major champion and former number one in her own right, was playing spectacular tennis, too, nearly the equal of Williams in every facet.

Nearly.

For when Williams finds her best game, she becomes unbeatable. And for her past 26 Grand Slam matches she is, indeed, unbeaten. Erasing an early deficit at Centre Court, Williams got past Azarenka 3-6, 6-2, 6-3 on Tuesday with the help of 17 aces and a remarkable ratio of 46 winners to 12 unforced errors.

She is closing in on a fourth consecutive major title for a self-styled Serena Slam, which she already accomplished in 2002-03. Pull that off, and Williams also will have the third leg of a calendar-year Grand Slam and go to the U.S. Open with a chance to become the first player since Steffi Graf in 1988 to win all four major trophies in one season.

In today’s semifinals, number one, Williams, faces number four, Maria Sharapova, who beat unseeded American CoCo Vandeweghe 6-3, 6-7 (3-7), 6-2.

Williams is 17-2 against Sharapova, including 16 straight victories. But one of Sharapova’s wins came at Wimbledon, in the 2004 final, when at age 17 she stunned Williams for the first of her five Grand Slam titles.

“Definitely no secrets between each other’s games,” Sharapova said.

Williams, whose major trophy count is at 20, said of the matchup: “I look forward to it.”

Here was the scouting report from Williams’ coach, Patrick Mouratoglou: “If she plays like today, I don’t think anyone can compete.”

The other semifinal is number 13, Agnieszka Radwanska of Poland, against number 20, Garbine Muguruza of Spain.

Britain’s Andy Murray reached his sixth Wimbledon semi-final in seven years with victory over Canadian Vasek Pospisil under the Centre Court roof.

The Scot, seeded third, won 6-4 7-5 6-4 in two hours and 13 minutes, and will play second seed Roger Federer in the last four tomorrow.
Murray, 28, had to cope with two rain delays, the second of which saw the roof brought across in the second set.

“It was difficult, we were stopped a couple of times,” said Murray.

“I hope I can get to another final but it’s going to be difficult.”

Murray produced a clinical performance to see off Pospisil, the world number 56, in straight sets.