Millwall boss Neil Harris insisted there would be no complacency from his side heading into the second leg of their League One play-off semi-final tie against Bradford next Friday.
The Lions will be strong favourites to advance to the final at Wembley on May 29 after coming from behind to win 3-1 at Valley Parade on Sunday afternoon.
Tony McMahon gave Bradford an early lead but Millwall responded almost immediately through Lee Gregory’s 26th goal of the season.
Steve Morison put Millwall 2-1 up in the 34th minute when he headed Shane Ferguson’s corner past Ben Williams, before Joe Martin’s free-kick made it 3-1 before half-time.
Phil Parkinson’s side dominated the second half and should have pulled a goal back but Filipe Morias dragged a shot wide of an open goal after Jamie Proctor had robbed Carlos Edwards of possession.
The Bantams had a number of set-piece opportunities but Byron Webster and Mark Beevers were again immense against the physical threat of Proctor and later substitute Steven Davies.
Parkinson admitted afterwards his side weren’t used to being behind. Harris, meanwhile, was pleased with how Millwall responded to going a goal down but warned the tie isn’t over.
“It’s all the old clichés, it’s only half-time and the boys have to prepare mentally and physically for the second leg,” Harris said. “I’m delighted with the result and character.
“I thought we saw the real Bradford side in the second half and how difficult they made it for us. They imposed themselves on us. But we’re really pleased with the day’s work.
“I think at our football club character and team spirit and desire are key words for us. We’ve had to try and instil that and build that over the course of the season.
“There were two things for me today, coming from a goal behind in such a brilliant atmosphere, to come from a goal down so quickly was brilliant, for my players to focus in such adversity and come through that. And then in the second half when Bradford were better than us we stood strong and trusted in our shape.
“We were reliable and threw ourselves in front of efforts on goal. And then we had the quality with those three goals.”
Harris expects Bradford to play with freedom next week as they bit to overturn the deficit, but the Lions boss stressed his side will be ready for the reaction to Sunday's loss.
“They can play with spirit and the first goal will be key,” Harris said. “But there will be no complacency from my group, that’s for sure. We don’t have that. We have too much character in the team to have that.
“We know it will be difficult. Bradford will get the ball forward and try to put us under pressure, especially early on.
“We’ll rely on our shape, as ever, and we trust each other. And we will rely on a really strong atmosphere at The Den on Friday night.”
Harris confirmed after the game he had taken off Gregory as a precaution just a few weeks after the striker had surgery on his hernia.