Maria Sharapova looked out of sorts after surrendering an early advantage as she was stunned 4-6 6-4 6-3 by Romanian qualifier Monica Niculescu in the Qatar Open first round.
Wild card Sharapova, playing in Doha for the first time since 2013, looked on course for victory after taking the first set.
But she struggled to carry forward the momentum against a determined opponent and crashed out after two hours 38 minutes.
Five-times Grand Slam winner Sharapova was not helped by 11 double faults and 52 unforced errors while her opponent, who fired 12 winners, grew in confidence as the contest went on.
Qualifier Niculescu used her slices to good effect and converted six out of seven break points in the match to oust Russian Sharapova.
She will now take on Wimbledon semi-finalist Magdalena Rybarikova or local wild card Fatma Al Nabhani next.
Earlier, Dominika Cibulkova rallied past Russia’s Anastasia Pavlyuchenkova 7-6(8) 6-4 as she progressed to a second round meeting with France’s seventh seed Caroline Garcia.
Romania’s Mihaela Buzarnescu eased past Lesia Tsurenko to set up a clash with sixth-seeded French Open champion Jelena Ostapenko.
American qualifier CiCi Bellis advanced after Daria Kasatkina pulled out of their opener with an injury.
Russians Ekaterina Makarova and Anna Blinkova aslo reached the second round.