Luke Hannant’s 29th-minute goal has given Colchester United an unlikely 1-0 half-time lead over the Blues in the Carabao Cup first round at Portman Road.
Town boss Kieran McKenna made the expected wholesale changes with only Cameron Burgess remaining from Saturday’s 2-1 win at Forest Green Rovers.
Vaclav Hladky was in goal with former U’s defender Kane Vincent-Young on the right of the back three with Luke Woolfenden returning in the centre having been ill at the weekend with Burgess on the left.
Kyle Edwards and Greg Leigh were the wing-backs with Cameron Humphreys and Rekeem Harper in the centre of the midfield.
Sone Aluko, who skippered, and Tyreece John-Jules started behind lone striker Kayden Jackson.
For Colchester, ex-Blues Luke Chambers, who captained, Cole Skuse, Tom Eastman and Frank Nouble were all in the starting line-up.
The U’s, whose head coach is former Town defender Wayne Brown, made four changes from the team which drew 1-1 with Carlisle on Saturday, while three players were making first starts. Tommy Smith and Emyr Huws were out injured, while Freddie Sears appeared to pick up a knock on Saturday and Alan Judge is understood to have been rested.
Ahead of kick-off both teams - other than Aluko - took a knee to applause from the sparse crowd with the upper tiers of the Sir Bobby and Sir Alf stands closed.
Aluko created the evening’s first opportunity, playing a low ball in for Humphreys but the young midfielder scuffed his shot through to visiting keeper Sam Hornby.
On three, wing-back Leigh was found on the left of the box but he similarly failed to make significant contact and Hornby claimed.
Town dominated the early stages with Colchester unable to get out of their penalty area with the Blues’ centre-halves sitting midway inside the visitors’ half.
On seven, Harper crossed towards the back post but a Colchester defender dived to head away in front of Leigh, then a minute later the former Morecambe man cut in and hit a shot which wasn’t enough to trouble Hornby.
The Blues continued to have all the possession and in the 14th minute, following a free-kick, Humphreys smashed a shot which sent Ossama Ashley sprawling.
The Town pressure dropped in its intensity as the game reached the 20-minute, although with the Blues still well on top. On 21 a headed clearance fell to John-Jules, who sent a volley well into the stand.
Three minutes later, the on-loan Arsenal man sought to sweep a low near-post corner goalwards but only found the side-netting.
Town should have taken the lead in the 26th minute when Aluko played in Edwards with a clever ball to the right of the area and the former West Brom man cut it back to Humphreys, who seemed destined to score his first senior goal but blazed over from 12 yards.
Two minutes later, having spent virtually no time in the Town half let alone the penalty area, the U’s went ahead following a catastrophic mix-up in the Blues’ defence.
Harper played a pass into his own area from the right between Burgess and Leigh and Luke Hannant gleefully seized upon it and smashed past a startled Hladky to give the visitors an unlikely lead.
On 35, the game was held up after a smoke bomb was thrown on to the pitch by Colchester supporters, the second of the evening following one at kick-off.
The Colchester goal and its manner appeared to discombobulate the Blues and give the U’s confidence.
In the 38th minute, former Blues midfielder Skuse was shown the game’s first yellow card for a foul on Harper.
From the free-kick, Town, who had got back on top although while still a little nervy with John-Jules now down the centre having swapped with Jackson, created a chance, Humphreys crossing from the left but Vincent-Young was unable to keep his header down.
On 40, Humphreys had another great opportunity, the youngster having been picked out by Vincent-Young just beyond the penalty spot but the academy product scraped his shot wide. The 18-year-old, playing the Sam Morsy role in central midfield, had got into some excellent positions throughout the half but had been unable to take his chances.
Town were unable to threaten again before referee Sam Purkiss blew his whistle. The Blues had dominated almost from start to finish and had created plenty of opportunities but had been unable to take them, the best having fallen to the otherwise excellent Humphreys.
Colchester’s goal came from their only chance of the half, Hannant making the most of Harper’s sloppy pass across his own area. Having been knocked out of their rhythm after conceding, the Blues restored their control but still with an element of nervousness about their play.
Town: Hladky, Vincent-Young, Woolfenden, Burgess, Edwards, Humphreys, Harper, Leigh, Aluko (c), John-Jules, Jackson. Subs: Hayes, Edmundson, Donacien, Penney, El Mizouni, Evans, Burns, Chaplin, Harness.
Colchester: Hornby, Chambers (c), Hannant, Skuse, Chilvers, Ashley, Eastman, Tchamadeu, Kazeem, Miranda, Nouble. Subs: Collins, Clampin, Dallinson, Newby, Akinde, Coxe, Tovide. Referee: Sam Purkiss (Surrey).