Briton Emma Raducanu is through to round three at Indian Wells after opponent Dayana Yastremska retired with an injury in the opening set.
Raducanu, 21, raced into a 4-0 lead in just 18 minutes during the first set.
Ukrainian Yastremska stepped to the back of the court between games, holding her stomach before retiring from the contest after being assessed by the medics.
Raducanu will face Peyton Stearns or Aryna Sabalenka in round three.