It was raining, ever so slightly, and her Wimbledon fourth-round match was slipping away, ever so slightly, when Serena Williams stumbled as she ran to the net, winding up seated on the slick Centre Court grass.

Her opponent, two-time major champion Svetlana Kuznetsova, sent a shot flying past Williams to go up a break at 5-4 in the opening set.

Williams was slow to get up. She wasn’t injured, but was worried she could be. Why, she demanded to know from chair umpire Marija Cicak, wasn’t the retractable roof shut? Eventually, after one more game and much discussion, action was delayed for nearly 30 minutes while the cover was closed.

Whether it was the transformation to an indoor court, the strategy session the break allowed her to have with coach Patrick Mouratoglou or, as Williams suggested, simply the chance to calm down, she completely dominated the rest of the way, taking the last nine games to beat the 13th-seeded Kuznetsova 7-5, 6-0 on Monday.

“I’m so intense on the court. I give 200 percent every time I’m out there. Every single point. Sometimes I just need to take a deep breath and relax. I just needed to do that. I can do that on the timeouts,” said Williams, who is seeking her seventh Wimbledon title and 22nd Grand Slam trophy overall.

“That’s one thing the past four years I’ve been really doing a lot of, just really taking a deep breath, re-collecting myself,” the No. 1-ranked Williams continued. “I had a little more time to do it this time.”

She wound up winning 24 of the match’s last 29 points, and her 14 aces helped produce a “Did I read that right?” edge of 43-8 in winners.

The 13th-seeded Kuznetsova said she knew closing the roof would help Williams, but agreed it was the right decision, given how wet the grass was, saying: “I was afraid. … I’m not ready to risk (an) injury.”

Williams moved into her 12th quarterfinal at the All England Club, and she’ll be joined by her older sister Venus at that stage of the tournament for the first time since 2010.