Nesta Guinness-Walker’s 41st minute goal has given AFC Wimbledon a 1-0 half-time lead over Town at Portman Road.
Skipper Luke Chambers dropped to the bench as Blues boss Paul Lambert made three changes for the first ever visit of AFC Wimbledon.
James Wilson came into the back four alongside Luke Woolfenden with Janoi Donacien and Myles Kenlock the full-backs and Tomas Holy in goal.
Lambert switched to a central midfield three with Andre Dozzell making his first League One start of the season alongside Flynn Downes and Cole Skuse, who wore the captain’s armband.
In the front three, Idris El Mizouni started for the first time this season on the left with Danny Rose on the right and James Norwood in the centre.
Gwion Edwards and Kayden Jackson also dropped to the bench, alongside new loanee Anthony Georgiou. Kane Vincent-Young missed out, presumably due to the toe injury he was suffering from at the weekend.
For AFC Wimbledon, ex-Blues Shane McLoughlin and Dylan Connolly were among the subs, while there was a late change of referee with Antony Coggins taking over from Robert Jones.
The first 20 minutes passed uneventfully with neither team creating an opportunity. The Blues had had spells of possession without hurting the Dons, but more of the game had been in the Town half, although with the visitors equally unable to conjure a chance against the home backline.
A short spell of head tennis on the edge of the box led to an opening for Norwood in the 29th minute, Rowe hooking the ball into the area in front of the former Tranmere man but he scuffed his strike and El Mizouni was unable to reach the loose ball ahead of Wimbledon keeper Nathan Trott.
Four minutes later, Downes chipped a cross towards Norwood from the right but beyond the Town striker.
After their slow start, the Blues gradually began to put the Dons under pressure, winning back-to-back corners in the 35th minute. From the second, Skuse headed goalwards but Trott claimed.
A minute later, they shoud have gone in front. Dozzell played Norwood in on goal with a trademark threaded pass and the striker seemed set to score his first goal at Portman Road but Trott stood up well and forced it wide.
The Blues seemed to be getting on top, however, it was Wimbledon who would take the lead with their first serious shot of the evening.
Following a counter-attack, Michael Folivi held off his man with his back to goal on the edge of the box, then fed Nesta Guinness-Walker, who was breaking from deep on the left unchecked, and he smashed a shot past Holy to his left.
Town were unable to create another chance before the break with the whistle greeted by loud boos from the home support.
The Blues had started slowly but seemed to be find their feet as the half moved into its final 10 minutes with Norwood’s chance one the frontman will feel he should have taken.
However, they were caught by a sucker punch with the Dons breaking and then Guinness-Walker in acres of space as he joined the attack on the left and beat Holy with his low strike.
Town, with new loanee Georgiou preparing to come on at the restart, will need to be significantly better in the second half if they’re to take the expected three points from the game.
Town: Holy, Donacien, Woolfenden, Wilson, Kenlock, Skuse (c), Dozzell, Downes, El Mizouni, Rowe, Norwood. Subs: Norris, Chambers, Edwards, Jackson, Judge, Georgiou, Huws.
AFC Wimbledon: Trott, O’Neill, Thomas, McDonald, Kalambayi, Guinness-Walker, Reilly, Hartigan, Wagstaff (c), Folivi, Appiah. Subs: Tzanev, Roscrow, Pinnock, Connolly, McLoughlin, Osew, Pigott. Referee: Antony Coggins (Oxfordshire).