Bethanie Mattek-Sands beat Vera Dushevina of Russia 6-4,6-4, in the opening round of the BNP Paribas Open at the Indian Wells Tennis Garden on Wednesday.
Mattek-Sands called for the trainer while leading 6-4, 4-3. She seemed to be favoring her left side during the seventh game.
The match resumed after a lengthy delay that also included a visit from the WTA doctor.
Mattek-Sands said she was battling an upset stomach because "I just got sick. I was throwing up a little bit. It came on during the second set. I played in Dubai (in mid-February) and got sick there and when I came home I was in bed for a week and a half. I only had a couple of days of practice before I got here."
Mattek-Sands said she never considered retiring from the match.
"I would have thrown up on the court first," she said. "I was just going to gut it out."
She did that by breaking Dushevina's serve twice.
The win by Mattek-Sands was one of three for the Americans.
Coco Vandeweghe also moved into the second round by beating Edina Gallovits-Hall of Romania, 4-6, 6-3, 6-4, in a 2-hour, 23-minute match and Melanie Oudin closed out the session with a 7-6 (2), 6-2 win over Elena Vesnina of Russia.
In other matches involving U.S. players, Vania King, a wild card entry ranked No. 100, was beaten by Gisela Dulko of Argentina, 2-6, 6-3, 6-2 and Lauren Davis, a 17-year-old wild card, lost to Zuzana Ondraskova of the Czech Republic, 6-2, 6-1; and Alison Riske, another wild card, fell to Barbara Zahlavova Strycova of the Czech Republic 6-2, 6-1.
No. 32 Lucie Safarova of the Czech Republic, the highest-ranked player on the schedule, outlasted Kristina Barrois of Germany, 7-6 (9), 6-7 (5), 6-0. Alla Kudryavtseva of Russia, Anastasija Sevastova of Latvia, Timea Bacsinszky of Switzerland, Kimiko Date-Krum of Japan, Sybille Bammer of Austria, Monica Niculescu of Romania, Sania Mirza of India and Sara Errani of Italy also advanced.