Joe Ledley admits it took a half-time tongue lashing from manager Neil Lennon to really kick the players into gear yesterday.
The Hoops found themselves 0-0 at the break against ten-man Dundee United, who had Robbie Neilson sent off in the 28th minute, in their Scottish Cup quarter-final but eventually overhauled the Tangerines to record a 4-0 away victory.
Welsh winger Ledley, who netted Celtic's opening goal eight minutes into the second half, said it was some harsh words from Lennon that got the team up and about and still in with a chance to win the Scottish treble.
"We knew we had to get on the ball, get it to our forward players and work off them.
"Thankfully that happened. At the end he was delighted with the way we bounced back."
He added: "Everyone wants to take a piece of us and Dundee United fancied the game.
"If we play like we played in the first half there will be no Treble.
"I didn't think we were anywhere near where we can be first half and that's credit to Dundee United. They were quicker to the ball and looked the hungrier team. I thought we could have played a lot better.
"The scoreline probably flattered us. But I can't complain, we're in the semi-final.""The manager wasn't happy with our first half performance and made it clear at half time. We went back out a totally different team," Ledley said.