Garbine Muguruza refused to let the rain in Rome disrupt her march to victory over Sloane Stephens.

The Spaniard prevailed 6-3 6-3 in a battle between two grand slam winners to reach the second round of the Internazionali d'Italia.

But the ninth seed had to wait out a downpour she had not seen coming before she could seal the win and a meeting with Coco Gauff.

"It was unexpected, because I checked the weather and it seemed like it was okay," she said of the interruption, which delayed the start of the second set by an hour.

"But I just had to adapt. I knew I had a tough match against Sloane, she's also a great player on clay.

"I'm just happy with my performance, since this is the third match I am able to play in a long time."

There was a shock exit for three-time grand slam champion Angelique Kerber as she fell to 6-3 6-1 loss against Katerina Siniakova.

Gauff defeated Ons Jabeur 6-4 6-3 to progress, with the 16-year-old joined in the next round by 12th seed by Marketa Vondrousova following her three-set triumph over Misaki Doi.

Elsewhere in the draw, 14th seed Anett Kontaveit overcame Caroline Garcia 6-3 7-6 (7-1), while two-time slam champion Svetlana Kuznetsova came from a set down to beat Bernarda Pera.