Britain's Andy Murray was unable to back up his first win of 2024 as he lost to 18-year-old Jakub Mensik in a rollercoaster Qatar Open match.
Murray ended a run of six defeats by beating Alexandre Muller on Tuesday but lost 7-6 (8-6) 6-7 (3-7) 7-6 (7-4) to world number 116 Mensik 24 hours later.
Trailing 5-2 in the decider, the Scot, 36, clawed back both breaks as his Czech opponent could not serve out.
However, Mensik reset mentally to win and reach his first ATP quarter-final.
Murray's frustrations were clear as he made a sharp exit after a tense contest lasting three hours and 23 minutes - the longest match in the Qatar Open's history.