Emma Raducanu was compelled to withdraw from her Qatar Open first-round encounter against Camila Osorio after receiving medical attention on court in Doha.
The British player, currently ranked 25th in the world, had claimed the opening set but saw her form deteriorate as the match progressed.
When Raducanu pulled out, the Colombian world No 80 held a 2-6, 6-4, 2-0 advantage.
A doctor attended to the 23-year-old during the contest, with concerns mounting about her physical condition following a demanding schedule in recent days.
Emma Raducanu was forced to retire in the third set against Camila Osorio
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The retirement brings an abrupt end to what had been a promising start to the WTA 1000 tournament.
Attention had been firmly fixed on Raducanu's physical state heading into this Doha fixture, given she had competed in the Transylvania Open final merely 48 hours earlier.
That Cluj showpiece against Sorana Cirstea proved a difficult afternoon for the Brit, who suffered a comprehensive 6-0, 6-2 loss in her first tour final since capturing the 2021 US Open title.
Following that defeat at the WTA 250 event in Romania, Raducanu had referenced concerns about her health.
The heavy nature of that loss to Cirstea suggested the 23-year-old was operating well below her best level, raising questions about whether she should have travelled to Qatar so quickly.
Emma Raducanu had looked in fine fettle before injury struck, proving more frustration
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Despite the fitness concerns, Raducanu appeared sharp and energetic during the early stages against her Colombian opponent.
The Brit had previously defeated Osorio at the Hobart International last month, and she carried that confidence into the opening set in Doha.
Raducanu secured three breaks of serve while conceding just one, establishing clear dominance in that first set.
The second set told a different story, with the 23-year-old immediately facing pressure on her service games.
Osorio required only a single break to level the match and force a third set.
After losing her serve in the decider's opening game, Raducanu had her blood pressure monitored by medical staff before ultimately withdrawing.
Raducanu's withdrawal represents a significant setback given the positive momentum she had built in Cluj.
Emma Raducanu was completely outplayed by Sorana Cirstea in their Transylvania Open clash | GETTYThe 23-year-old climbed five positions to reach world No 25 on Monday, marking her highest ranking since September 2022.
A deep run at this first WTA 1000 event of 2026 could have propelled her even higher in the standings.
She remains provisionally positioned at world No 24 in the live rankings, though other competitors may overtake her during the remainder of the tournament.
The pressing question now centres on whether Raducanu will recover sufficiently for the Dubai Tennis Championships, the second consecutive WTA 1000 event in the Middle East beginning next week.