Raducanu struggled under the lights on the stadium court in the Southern California desert on Friday with her accuracy and energy level.
Stefanos Tsitsipas dismissed 44th-ranked Frenchman Adrian Mannarino, ducking both the heavy rain and his opponent’s offbeat lefty game.
The 20-time Grand Slam champion is through to the second round after Mannarino called it quits at the start of the fifth set.
The 20-time Grand Slam champion is feeling “pumped up” as he is targeting to reach the second week of Wimbledon.
Thiem was leading the opening set 5-2, but appeared to injure his right wrist when he struck a forehand. Elsewhere, Daniil Medvedev had it easy in his match.
The Spaniard teen, who will turn 18 on Wednesday, will take on his countryman in the second round of the Madrid Open.