Owen Coyle admitted he read the riot act to his team at half-time before launching substitutes Kevin Davies and Johan Elmander from the bench to guide Bolton past York in the FA Cup.
York, of the Blue Square Premier and 99 places beneath Bolton in the league rankings, were backed by almost 5,000 travelling supporters and fashioned the better chances of the first half.
They continued to create openings in the second 45 minutes, but Coyle's input, together with late goals from England striker Davies and Swedish frontman Elmander, helped Bolton sneak through to the fourth round.
Coyle revealed how he challenged his team following their tepid first-half display.
"I said, 'You'd better get your act together'," he explained.
"Because the way my team play we're not good enough at this stage of our development to think we can flick a switch and play at any given time.
"We have to play on the front foot with a real intensity for the whole duration of a match. Any less then we're always going to find difficult moments in a game, no matter who we play. We didn't have enough intensity in the first half.
"The introduction of Kevin Davies gave everyone a lift and when you're able to bring Matty (Taylor) and Johan into the fray you know there's real quality on the ball, and so it proved."
But the match remained in the balance until Davies struck from close range in the 83rd minute, with Elmander sealing the 2-0 win with a sweet 25-yard strike six minutes later.
Coyle said: "We're always delighted to get through in any cup competition. York City deserve great plaudits. Without sounding patronising I thought they were terrific.
"We were really the team who were on a hiding to nothing.
"Did we play particularly well? No. Did we score two great goals? Yes.
"And obviously I'm delighted we're in the hat for the next round."
York should have gone ahead a minute before Davies scored, but goalkeeper Adam Bogdan made a superb stop from midfielder Neil Barrett's low shot.
"When your chances come you have to take them. We did that today," Coyle said.
"Adam had the one terrific save. York applied themselves really well but I don't know if Adam had another save in the game."
Coyle was reluctant to discuss an interest in Middlesbrough centre-back David Wheater, who is understood to be in talks with Bolton about a move to the Reebok Stadium.
"I'm always loath to talk about other teams' players," Coyle said.
"What I would say about David Wheater is that he's a very talented young player, there's no doubt about that, but as I sit here I have not had any dialogue with Tony Mowbray, the manager of Middlesbrough, so I think that's where we are with that one."
York manager Gary Mills took charge at Bootham Crescent in October and has transformed the team's fortunes.
He almost saw his team produce a major cup shock, which he had predicted they were capable of doing.
"I'm gutted but proud of my team today," Mills said.
"The players kept going and I thought we were superb. We've been playing well in the league, and I told the players all week and today that I didn't want anything else, just for them to go out and play the way we have been.
"We haven't changed our shape for Bolton, we haven't changed the way we play, and we came very close, didn't we?
"We had the chance just before they scored.
"I'm gutted for everybody, but for me there's a lot of positives there, we're moving forward and starting to play well."
Mills suggested Davies had mis-hit his shot for the opening goal, and added: "I think anybody who was at the game today would say the least we deserved was a draw."