A triple change which saw Joe Ward, Ben Thompson and Jack Marriott come on at half time, when Posh trailed 2-0, along with a switch to wing backs from the 4-3-3 which Posh started with, was the catalyst to turn the match around.
Ward and Marriott combined for the first and Jonson Clarke-Harris sealed the three points with two further strikes, the second on which was also set up by Ward.
"I’m really proud of the boys, the character is never in question with this group, they proved that today and that is a benchmark for them.” He beamed after the full-time whistle.
He added: “The first half was probably the poorest I’ve seen us since I’ve been at the club. As a collective, we just didn’t get anything right.
“Cheltenham were good but we were well off the pace. The reaction in the second half was excellent from every single one of them.
“We changed the shape and maybe that caught Cheltenham off guard. Marriott, Thompson and Ward were sensational when they came on and they lifted the group, and I couldn’t be more pleased with the three points.
“Some of the balls Ward was putting in were outstanding, Josh Knight stepped in, the energy and aggression of Ben Thompson and the ability of Jack Marriott was clear to see. I was delighted and thoroughly deserved it given the fact we were much the better team in the second half.
“I’ve got an honest group; they were hurting at half time but I think they showed today what they can do when they step it up. I couldn’t be more proud of them.”
Posh also had 19-year-old Lucas Bergstrom to thank for the result on what was his senior debut in the Football League. He made a number of crucial saves including denying Alfie May with his legs on the stroke of half time and again with a tremendous outstretched left arm with the scores at 3-2.
McCann said: “He’s made three outstanding saves today, two particularly from Alfie May. The one he has made with his left hand was an unbelievable stop.
“You need that when you come to places like this. This is a tough place to come, they had a really good home record last year; that’s his league debut and he’s produced an unbelievable three saves to win us the game.”