Second seed Lucas Pouille had no trouble with qualifier Ernests Gulbis
Malek Jaziri thrilled fans at the Dubai Championships with a 4-6, 7-5, 6-4 first-round knockout of top seed Grigor Dimitrov to earn the biggest win of his career on Tuesday.
The Tunisian ranked 117 broke midway through the final set after fighting back to beat his first top 10 player.
The fourth-ranked Dimitrov was far from his best, perhaps still not fully recovered from the illness which bothered him this month as he lost the Rotterdam final to Roger Federer. He has also been bothered by a shoulder injury in recent months.
"You have days like this that you can't really do much else," Dimitrov said. "Unfortunately, I couldn't play my game to the extent that I was looking for.
"Movement was not good over the court. I thought I served okay for a little bit, but then I lost my rhythm again.
"All the credit to Malek. He played a good game, he was strong throughout the whole match. He had nothing to lose.
"Also pretty much a lot of luck was on his side, with the let calls. You control what you can control.
"Tonight, I couldn't control anything on my side."
Jaziri has a history in Dubai, facing major names including Federer -- he took a set off the Swiss in 2013 -- Novak Djokovic and Andy Murray, who beat him in the first round here a year ago.
"I just tried to enjoy the match and play my game," said Jaziri. "This is a fantastic result."
Wildcard Jaziri is playing the Dubai main draw for the sixth consecutive year, with a quarter-final run in 2014 his best showing.
Second seed Lucas Pouille had no trouble with the transition to outdoor hard court as he beat qualifier Ernests Gulbis 6-4, 6-4.
The Frenchman, a finalist indoors in Marseille on Sunday, wasted no time in acclimatising as he beat his Latvian opponent in 79 minutes.
"I knew it would be tough because I played only 20 minutes before the match," said Pouille, who flew in on Monday. "I arrived yesterday pretty late.
"I fell asleep around 4 or 5 a.m., so a bit tired. But I'm happy with what I did tonight.
"I've won many matches the past three weeks, so I'm arriving here with a lot of confidence. I think that helped me in the tough moments. Especially in the break points.
"I served pretty well and played good rallies. That's very positive."
Pouille said he never questioned his decision to play Dubai.
"I really wanted to come back because last year I had good feelings.
"I was playing well. I wanted to come and try to go as far as possible. I knew it would be tough. I know it's going to be tough tomorrow, as well. I'll try to give my best and go as far as possible."
Pouille's compatriot Richard Gasquet was hampered by a knee problem as he lost to Croatian Borna Coric 6-4, 6-3 earlier on Tuesday.
Coric, who beat Murray here in the quarter-finals three years ago, will next face another Frenchman, Benoit Paire, who beat Japan's Yoshihito Nishioka on Monday.
"I knew Gasquet was semi-injured, but I didn't know what to expect," the 50th-ranked Coric said. "I was really just trying to focus on myself."
Gasquet made the effort but was unable to get the win.
"He did come back in both sets, it was pretty good effort from him," Coric added. "But I managed to stay calm. I didn't panic. It was good."
Serbian seventh seed Filip Krajinovic beat Italy's Thomas Fabbiano 0-6, 6-2, 6-2, while Marseille champion Karen Khachanov defeated Denis Istomin 7-6 (7/1), 7-6 (7/0).