Serena Williams, who handily defeated Sloane Stephens in her second-round match in Madrid, said that there are several Spaniards to keep an eye on this spring. Last year, the current No. 20 Garbine Muguruza stunned Williams in the second round at the French Open, while Carla Suarez Navarro recently cracked the Top 10 for the first time. Both won their matches in Madrid on Sunday.

“They're playing really great,” Williams said. “Garbine is obviously playing great. She beat me on clay. She's someone I have to always look out for when I play her. Carla has done really well. She's been a clay-court player, but she's extended that beyond that now in the hard court now. I think that's also really exciting. It's good to have other countries like Spain that have been traditionally so good in tennis to be able to be really good again.”