Marin Cilic stunned by unseeded Malek Jaziri in Istanbul

Marin Cilic produced a poor performance as he crashed out of the Istanbul Open during his opening match of the tournament. Julian Finney/Getty Images

Marin Cilic got married last weekend but this was not the celebration he was after, as he suffered a shocking defeat at the Istanbul Open.

Defending champion Cilic fell lost in straight sets, 6-4, 6-2, to unseeded Malek Jaziri, who last week took world No. 5 Grigor Dimitrov to a third-set tiebreaker in the last 16 in Barcelona. World No. 88 Jaziri broke Cilic's serve five times on his way to securing a place in the quarterfinals Thursday.

In another upset, second seed Damir Dzumhur is also out after losing to Italian Thomas Fabbiano.

Dzumhur recovered from dropping the opening set to take the second with a bagel, but eventually succumbed to a 6-2, 0-6, 6-2 loss.

Jeremy Chardy is safely through to the last eight after he beat Dusan Lajovic 4-6, 7-6 (3), 6-2. Thiago Monteiro and No. 7 seed Jiri Vesely will face off in their round-of-16 clash.