He was going through a warm-up routine on the touchline when he stepped in front of Stuart Campbell as the Rovers' captain was trying to take a corner.
Referee Oliver Langford didn't spot it, but his assistant did and after a brief consultation out came a yellow card.
It was one of four for Colchester on a day they made hard work of taking an unbeaten run to seven games now worth 15 points.
Things began badly for them with Steven Gillespie limping out of the game with a stretched hamstring after only six minutes. They also lost - briefly - Kemal Izzet who needed to change his shirt after an aerial collision left him with a bloodied nose.
Scott Vernon was a ready replacement for Gillespie and in a game where the finishing never matched the approach work was the only one to get the ball in the net. His diving header just before half-time was ruled offside but it was a very tight decision.
The best move of a struggling first half came with the U's holding possession through a succession of passes, before Mark Yeates lifted a volley just wide of the keeper's left-hand post.
It was matched by Rovers who had much the better of the second half with a flowing build-up of passes which still left Jimmy Walker in the visitors' goal untroubled.
The one save came after 80 minutes when Steve Phillips in the home goal rescued an untidy personal performance with a brave save from Yeates, who had been played in by Izzet.