Top seed Grigor Dimitrov suffered a shock 4-6 7-5 6-4 to Tunisian wildcard Malek Jaziri in the first round of the Dubai Duty Free Tennis Championships on Tuesday.
Bulgarian world number four Dimitrov, who came into the event in good form having reached the final in Rotterdam last week, claimed the opening set with ease but failed to build on the momentum and lost in two hours and 17 minutes.
Jaziri, a quarter-finalist in Dubai four years ago, saved seven out of the eight break points he faced to seal the biggest win of his career. The world number 117 will take on Dutchman Robin Haase in the next round.
An ailing Richard Gasquet lost 6-4 6-3 to Croatian world number 50 Borna Coric in 75 minutes. The Frenchman played despite being hampered by a knee injury he picked up on Monday. Another Frenchman, Benoit Paire, is up next for Coric.
Lucas Pouille of France eased past Latvian Ernests Gulbis 6-4 6-4 to set up a second round match with Karen Khachanov, who beat him in the Marseille final at the weekend. Khachanov advanced with a 7-6(1) 7-6(0) win over fellow Russian Denis Istomin.
Also progressing to the second round were Serbia's Filip Krajinovic and eighth seed Yuichi Sugita.