Peterborough boss Darren Ferguson was relieved to see his side's play-off push get back on track after the euphoria of Sunday's Johnstone's Paint Trophy win against Chesterfield.
Posh saw off League One strugglers Colchester with a clinical display thanks to goals from Tommy Rowe and Britt Assombalonga.
Ferguson had allowed his Wembley cup winners to celebrate after the match but also warned them it was back to business for the clash against their East Anglia rivals.
He said: "We have always maintained what our two targets were [this season]. One of them has gone, we've got that out of the way and won it. But the main one has always been promotion.
"If we can get a consistent level of performance like we have seen tonight then we are a hard team to play against. Everyone in our league knows that.
"So I am not going to get carried away with one performance but I have to say that I am delighted.
"After Sunday we all understood the importance of this game. I think the players really responded to that and everyone has gone home happy.
"I thought we were very good, on and off the ball. The players did exactly what we asked of them. We were dominant and I couldn't really fault anyone. All 14 players played a part.
"It was as comfortable as it's been for a long time and the level of performance throughout the team was very good."
Posh skipper Rowe headed the hosts in front from a Grant McCann corner on 26 minutes.
More chances went begging as Peterborough dominated but they had to wait until the 65th minute for Assombalonga to seal the win.
The Posh striker robbed Colchester defender Magnus Okuonghae and drilled in a low shot that beat Sam Walker.