Emma Raducanu's time in Indian Wells was cut short on Sunday evening, as she suffered a 6-7(3) 6-4 7-5 defeat to Petra Martic.
Martic started brightly and broke Raducanu in the first set, only for the world No.11 to take a 5-3 lead after some impressive rallies.
Raducanu then served for the opener but struggled to capitalise on the opportunity, eventually having to settle for a tie-break.
The pair then traded breaks in the second set but world No.79 Martic saved a crucial break point before holding her serve to win 6-4 and set up a dramatic decider.
Despite being broken early on in the third set, Raducanu pieced together a superb run, winning five of the seven games that followed Martic's break.
That put Raducanu within touching distance of the win, but Martic - who reached the quarter-finals four years ago - mounted a comeback to book her spot in the round of 16.
Following the match, Raducanu pointed towards her lack of preparation heading into the tournament.
"I think it's just part of not playing and having so much stop-start and having five, six days to prepare for matches and then playing at that intensity.
"It was a tough one not being able to serve full out so I was having to work so hard just to hold. I've just got to get stronger.
"I've had it for the last few days, just a product of training hard and probably the last match was pretty intense too and it didn't settle down.
"When you are crossing your fingers to hold serve every time, it's tough. I couldn't really drive up and I was kind of struggling to turn and reach. The margins were so small."
Up next for Martic is world No.28 Ludmilla Samsonova in the round of 16.