Klasnic scored the winner in Wednesday's fourth-round replay against Wigan and he was on target again today as Bolton beat Fulham 1-0 at Craven Cottage to book a trip to Birmingham.
Greater Manchester Police have confirmed that Klasnic will not face charges over the alleged rape of a teenage girl, following an investigation dating back to October.
Coyle, the Bolton manager, said: "We are delighted the news broke there would be no case to answer.
"We knew from the outset he had done nothing wrong. Ivan was in a bad position because we couldn't really say anything because of the extent of what was involved.
"A lot of people look up to Ivan because of his fanbase in Croatia and Germany and the level he has always played at. Ivan is a natural goalscorer. There is still more to come from him."