Cameron Norrie failed to move past the first round of the BNP Paribas Open in Indian Wells after losing to Felix Auger-Aliassime.
The 23-year-old fell 6-3 6-2 to the wildcard in just over hour.
The Briton dropped behind on his first service game in the opening set and failed to convert a break point to get back on serve five games later.
Auger-Aliassime, of Switzerland, broke twice more in the second set and overall won 80 per cent of his first serve point to Norrie's 59 per cent.
Leonardo Mayer overcame wildcard Reilly Opelka to progress to the second round.
The Argentine battled past Opelka's big serve, prevailing 7-6 (8-6) 7-6 (7-2) despite facing 14 aces from the American.
Both players stayed on serve in the second set to force another tie-breaker, with Mayer outshining the world number 59 to wrap up the victory in one hour and 50 minutes.
Meanwhile, qualifier Marcos Giron, the world No 217, upset Jeremy Chardy, ranked 37th, overcoming the Frenchman 7-6 (7-3) 7-6 (7-1).
Elsewhere, Sam Querrey needed three sets to defeat Matteo Berrettini 7-6 (7-5) 2-6 6-4 and Jordan Thompson battled past Federico Delbonis 6-4 6-7 (6-8) 7-6 (7-5).
Former Wimbledon semi-finalist Kirsten Flipkens battled past Eugenie Bouchard to reach the second round of the women's tournament
The Belgian advanced after a three-set thriller lasting more than two-and-a-half hours, clinching the victory 7-5 3-6 7-5. She will now face 25th seed Danielle Collins.
Meanwhile, Venus Williams moved past Andrea Petkovic 6-4 0-6 6-3 to set up a second-round match against world No 3 Petra Kvitova.
Monica Puig, Madison Brengle and Kristina Mladenovic also advanced to the next round.
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