Michael Duff felt his Cheltenham side didn't apply any of the work his team had prepared for following a disappointing defeat at the JobServe Community Stadium.
The Robins were well beaten on their trip to Essex as goals from Kane Vincent-Young, Frank Nouble and Abo Eisa saw the U's record a league double over his side.
Speaking to the press after the full time whistle Duff believed the game serves as a reminder to his squad, with an opportunity to put things right with a trip to Grimsby Town's Blundell Park next weekend.
"The worst performance since I've been here," Duff said post-match. "We didn't head it, didn't pass it, didn't do anything we asked them to do so it's disappointing.
"Goals change games. The first goal is always important. You come away from home to a team trying to get in the play-offs and they'll see them as good goals but I thought they were really poor goals.
"We need to realise where we're at. We've not all of a sudden arrived and we've not all of a sudden become a good team - I keep telling people that.
"Yes we've gone eight points clear but not delivering performances like that. We might have got away with it in the last couple of weeks, we didn't today."
Watch more from Duff's post-match interview above on iFollow.
Read the match report from Colchester online here.