Earler, Cilic was given a code violation by Carlos Ramos – the umpire who was called a “thief” by Serena Williams in the US Open final for smashing his racquet.
The world number six broke his racquet on the ground after a series of errors in a tight third set against Querrey.
He was given the reprimand by Ramos but, because it was his first offence of the match, Cilic was issued with a warning and no points were deducted.
“Usually when you break a racquet, you get a code violation,” Cilic said, adding that he “could not remember” the last time he broke any equipment on court.
The 29-year-old had previously squandered a 6-1 lead in the second set tie-break and hit 72 unforced errors to Querrey’s 57.
There was further frustration for Coric, who led 5-1 in the third set which he eventually lost on a lengthy tie-break.
However Coric, who beat Roger Federer in the Halle Open final in June, took control of the final two sets to win in four hours and six minutes.