Ched Evans’s goal five minutes before the break has given Fleetwood a 1-0 lead over the Blues at half-time.
Brett McGavin was handed his league debut and Andre Dozzell returned to the side for the first time in two months as Paul Lambert made six changes.
McGavin was in the deeper midfield role behind Dozzell, whose last first-team game was the Leasing.com Trophy tie at Exeter at the start of January, alongside Jon Nolan, with Cole Skuse and Emyr Huws, starters during the 2-1 defeat at Blackpool on Saturday, missing due to a gash on the shin and a toe injury respectively.
Tomas Holy continued in goal with the Blues returning to a back three with - from the right - James Wilson, skipper Luke Chambers and Josh Earl the centre-halves. Janoi Donacien and Luke Garbutt were the wing-backs. Will Keane was up front with Alan Judge set to play off him.
Teddy Bishop and Freddie Sears were among the subs, having made their first starts of the season at Bloomfield Road, as were young duo Tyreece Simpson and Armando Dobra.
Flynn Downes missed the first game of his two-match ban for reaching 10 bookings and Kayden Jackson the second of his three-game suspension.
Fleetwood, at Portman Road for the first time in their history with manager Joey Barton in the stands serving a touchline ban, named an unchanged team from last week’s 1-1 draw at Sunderland.
Neither side threatened in the early stages with Fleetwood seeing most of the ball but without threatening. On 15 Paddy Madden shot well wide from the left of the area.
Moments later former Town loanee Callum Connolly was switched for Evans, back from suspension, the on-loan Everton man having been on the sidelines having a nosebleed attended to for the previous few minutes.
Chances continued to be non-existent at both ends with Fleetwood having most of the possession but without threatening and the Blues struggling to get on the ball. In their rare spells with it there were one or two neat interchanges involving Dozzell, McGavin and Judge but without getting near to creating an opportunity.
On 28 the visitors weren’t too far from opening the scoring in slightly fortunate circumstances when Barrie McKay was found in space on the left and his cross was diverted off the outside of the near post by Chambers from six yards.
Despite their possession, Fleetwood had threatened very little but in the 40th minute they went in front. McKay played in sub Evans who took it on in to the area on the left before hitting a shot beyond Chambers’ dive, across Holy and into the net.
The Fleetwood goal prompted boos from the previously sullen Town crowd, followed by chants of ‘you’re getting sacked in the morning’ aimed towards manager Lambert and ‘Marcus Evans, get out of our club’.
Fleetwood taking the lead seemed to wake the Blues up, Dozzell playing in Donacien on the right of the box but the right wing-back’s low cross was blocked.
In injury time, McGavin and Dozzell cleverly combined to find Keane in the penalty spot following a corner but the striker was crowded out before he could get in a shot.
The half-time whistle was greeted by more boos after a woeful first period from the much-changed Blues.
Town, looking utterly bereft of confidence and dynamism, had struggled to get hold of the ball throughout the half with Fleetwood dominating possession although to little effect until their goal five minutes before the break.
The Blues will have to be much, much better if they’re to avoid a defeat which would make even a play-off finish a tall order in the final nine games of the season and put manager Lambert under even greater pressure. A number of changes at the break would be little surprise.
Town: Holy, Donacien, Earl, Chambers (c), Wilson, Nolan, Judge, Dozzell, Garbutt, McGavin, Keane. Subs: Norris, Edwards, Bishop, Sears, Woolfenden, Dobra, Simpson.
Fleetwood: Cairns, Coyle, Andrew, Connolly (Evans 16), Souttar, Burns, Whelan, Coutts (c), Madden, Gibson, McKay. Subs: Crellin, Morris, Thervaldsson, Sowerby, Saunders, Holgate. Referee: Neil Hair (Cambridgeshire).