Video highlights: Russian Evgeny Donskoy, Serb seventh seed Filip Krajinovic and Tunisian wild card Malek Jaziri all advanced
Lucas Pouille won a re-run of the weekend Marseille final, beating Karen Khachanov 6-4, 3-6, 6-3 on Wednesday at the Dubai Championships.
The Frenchman was the only player from his nation to win on the day from three on court.
Benoit Paire lost 6-1, 6-4 to Borna Coric while Pierre-Hugues Herbert fell to Spanish third seed Roberto Bautista Agut, 6-4, 6-7 (2/7), 6-1.
Bautista Agut and Coric will meet in the quarter-finals.
Japan's eighth seed Yuichi Sugita beat German Jan-Lennard Struff 7-6 (7/4), 6-4 and will face Pouille in the last eight.
On Sunday, Khachanov edged Pouille in the third set in the Marseille final, but the Frenchman struck back at the Aviation Club in Dubai.
"In the Marseille final, he won just three points more than me," Pouille said. "I knew it was very close. I had to play some good tennis."
"We were both I think a little bit tired. I'm just very happy that I got my revenge today."
Paire's racquet disintegrated in the second game against Coric but it wasn't the only thing to fall apart as he lost in 63 minutes, serving seven double-faults and dropping serve five times.
Bautista Agut needed almost two and a half hours to advance as Herbert forced a third set tiebreaker.
"I had to fight so hard, it was tough to feel good on the court today," said Bautista Agut, ranked number 23 in the world. "There was a lot of wind, it was not easy to play."
Russian Evgeny Donskoy, who upset Roger Federer at the tournament a year ago in the second round, hammered fourth seed Damir Dzumhur 6-1, 6-1.
Serb seventh seed Filip Krajinovic defeated popular Cypriot Marcos Baghdatis 7-6 (7/2), 6-4 and young Greek Stefanos Tsitsipas stopped Geman Philipp Kohlschreiber 4-6, 6-3, 6-4.
Tunisian wild card Malek Jaziri, who beat top seed Grigor Dimitrov in the first round, advanced over Robin Haase 7-6 (7/4), 7-6 (7/3), saving all eight break points he faced.