Garbine Muguruza finally gets big win again, even though by retirement

INDIAN WELLS, Calif.—The 25-year-old from Spain won her third round match against Serena Williams at Indian Wells, with Williams calling it quits during the second set because of illness.

But it was still the biggest name the two-time Grand Slam champion has defeated for a while. A poor 2018 season has dropped her to No. 20 in the rankings—though Muguruza says she doesn't pay attention to that.

"You know, it's going to sound weird, but I don't really look at it. I don't really care—of course if you're higher, it's better, but I realize that today Serena, I think, is No. 10," she said. "Nobody cares, you know. You're facing good players."

According to Muguruza, the difference between being a top-ranked and lower-ranked player is largely down to making a few more errors—"choosing right shots, or a little bit of confidence, it's a mix between not playing enough matches, maybe not facing enough the top players."

But Muguruza, who also reached the fourth round of the Australian Open, has being doing some extra training to turn this around this season.

"I did a lot of work in my body, in the tennis. I work harder to kind of come back and be stronger."