Klasnic sealed a 1-0 triumph in the fourth-round replay at the DW Stadium in the 66th minute, collecting Mark Davies' pass and smashing a shot beyond Latics goalkeeper Mike Pollitt. With Sturridge cup-tied, Klasnic came in as one of six changes made by Coyle and was paired up front with Johan Elmander, as Kevin Davies dropped to the bench.
Coyle said: "I think we all know, he (Klasnic) had a couple of wonderful, gilt-edged chances in the first half and never took them, but that is the mark of a top striker - that they keep going and are prepared to miss, knowing that the door will fly open and they will score goals."
He added: "He did that and it was great. He was out on his legs at the end of the game, which I expected because of how hard he worked. His chances, as he knows because it has been stop-start with injury, have been limited.
"But as a manager, what a great problem to have, with the pairing that have played the last few games in the Premier League, Kevin Davies and Daniel Sturridge, not starting and Klasnic and Johan Elmander showing they are top players."
Coyle conceded his team might have done more with the opportunities that came their way, although he felt the poor state of the turf did neither team any favours.
"It was very pleasing the number of not just half-chances, but clear-cut chances that we created," Coyle said.
"As a manager that is what you want and the frustration is just that we never took as many of them as I would have liked. But it was a difficult pitch."