Dave Jones criticised his Sheffield Wednesday players despite their 4-2 victory at Oldham in the Capital One Cup first round on Monday.
The newly-promoted Championship side trailed 2-0 against their League One hosts at Boundary Park and needed a half-time rocket from Jones before they sparked into action.
Oldham took an early lead through Jordan Slew's debut goal and deservedly stretched their advantage with Jean Yves Mvoto's 26th-minute header.
Wednesday's Nejc Pecnik blazed wide from the penalty spot just before the break, Michail Antonio having been fouled by Lee Croft, but they were a different team after half-time.
The comeback was started by Jermaine Johnson's 18-yard effort after 58 minutes before another ex-Oldham player, substitute Chris O'Grady, netted with a header (61) and a shot on the turn (70).
Antonio completed the win three minutes from time with a fierce angled drive inside the far post from 18 yards.
But Jones said: "In the Championship we won't win many games from 2-0 down, if any at all.
"It's a hard league and, although we won tonight, there's still a lot of work to do.
"Maybe some of the players think they've arrived, but for 45 minutes they got their backsides slapped.
"We didn't close down, tackle or pass the ball. For 45 minutes we were well and truly out of it.
"Some words were said at half-time and they'll remain private, but I asked them nicely to go out and start playing like Sheffield Wednesday.
"They all deserve credit for coming back like that, but it's the first half I remember.
"It was by far the worst we've played in my time at the club and I was surprised by it.
"They responded to what we said but, believe me, I'm still spitting feathers."
Disappointed Oldham boss Paul Dickov said: "When we do things right with and without the ball, we're a decent team who play good football.
"But towards the end of the first half we got a bit giddy and we stopped doing the things that had helped us go 2-0 up.
"We knew Sheffield Wednesday would come out fighting after half-time and we lost our team shape when it happened.
"We stopped getting Jordan Slew in behind their defenders and we couldn't get players like Robbie Simpson and Lee Croft on the ball.
"We were excellent for most of the first half, but it has to be a 90-minute performance - in the second half Sheffield Wednesday did to us what we'd been doing to them.
"The goals we conceded were poor and we need to learn from tonight, but I suppose it's better for this to happen now instead of in the league."