Andrey Rublev saw off Mikhail Kukushkin to book a quarter-final clash against Pierre-Hugues Herbert on a day where other seeds struggled at the Qatar Open.

Second seed Rublev, a Doha finalist in 2018, eased to a 6-4 6-2 victory in 69 minutes on Wednesday.

They key moment of the match came late in the first set when he immediately broke Kukushkin back after the Kazakh had battled back to level the opening set at 4-4.

"I'm really happy that I could win in straight sets," Rublev said. "It was first match of the season, first match since two months, and, of course, I was a little bit nervous."

World number 23 Rublev will meet Herbert next after the Frenchman impressively knocked out number five seed Laslo Djere 6-1 6-3.

Miomir Kecmanovic defeated third seed Jo-Wilfried Tsonga 7-6 (11-9) 6-1, ending the Frenchman's hopes of repeating his 2012 title success.

Serbian Kecmanovic will next play Marton Fucsovics after the qualifier's straightforward win over wildcard Cem Ilkel.

Fernando Verdasco's three-set triumph over Filip Krajinovic means he will play Corentin Moutet, who recorded a straight sets victory against former Wimbledon finalist Milos Raonic.

Number one seed Stan Wawrinka, a loser in the doubles with partner Frances Tiafoe, takes on Aljaz Bedene in the last eight on Thursday.