New loan signing Omari Hutchinson created a second minute goal for Leif Davis but Saikou Janneh levelled for Cambridge United and home skipper Michael Morrison netted a final-minute winner as the Blues fell to their first defeat of pre-season at the Abbey Stadium.
Vaclav Hladky was in goal with youngster Ryan Carr, who signed from Carlisle in January, making his first start in the senior side at right-back, Leif Davis on the left and Luke Woolfenden and Cameron Burgess the centre-halves.
Lee Evans skippered in the centre of midfield alongside Massimo Luongo with Hutchinson on the right of the three behind striker Freddie Ladapo with Conor Chaplin and Marcus Harness alongside him.
League One Cambridge included on-loan Blues striker Gassan Ahadme, ex-Town men Paul Digby and Jack Lankester and one-time Playford Road academy schoolboy Ryan Bennett in their XI.
New boy Hutchinson was quickly into the action and in the second minute created a goal.
The on-loan Chelsea youngster exchanged passes on the right, worked himself space and then clipped over a cross for Davis, who scuffed a volley across home keeper Jack Stevens and into the corner of the net to give the Blues an early lead.
The game, played in persistent if not particularly heavy rain, briefly boiled over soon afterwards following an overzealous challenge on Chaplin on halfway by Blues academy alumnus Bennett. Ladapo and others were involved in some pushing and shoving before order was restored by referee John Brooks.
Town, who had found the U’s difficult opponents when they were at the Abbey Stadium in League One in February when the game ended 1-1, continued to threaten, Chaplin seeing two shots blocked and then a third fly wide.
On nine, last season’s 29-goal top scorer swept the ball wide to Hutchinson, who curled a delicate effort just beyond Stevens’s top corner.
In the 13th minute, a swift one-touch move which started in the Town area ended with Davis whipping over a cross which was just beyond Ladapo and the ball was turned behind. Within a minute, Harness sent over another ball from the same flank but again just in front of the Town number nine.
Five minutes later, Cambridge struck their first shot of the game after the Blues had played themselves into trouble not far outside their area, however, Janneh scraped his shot wide.
On 24, Janneh got to the byline past Carr on the left and crossed but the ball scuffed off Ahadme’s head and away from goal.
That chance may have gone begging but five minutes later, the home side did get on terms.
Janneh, who had provided most of their threat, broke forward down the left and struck a shot from the edge of the area which deflected off Burgess, looped over Hladky and under the bar.
With Town’s performance having drifted since the equaliser, Cambridge fans thought their side had taken the lead in the 36th minute when Janneh planted a header past Hladky but having strayed offside.
Chaplin shot high and wide a minute later as the Blues sought to regain their earlier control.
But the half ended with Town still off the boil having made a blistering start via Davis’s Hutchinson-created goal and a number of other chances.
However, the U’s began to create opportunities and were worth their goal when it came even if the deflection was a little fortuitous.
The home side were first to threaten after the break, Ahadme heading too close to Hladky, who claimed.
Town should have gone back in front in the 48th minute when Hutchinson did well to battle for a long Woolfenden ball out from the back and cut inside to Chaplin, who played Harness in on goal. The former Portsmouth man should have scored but Stevens saved and Davis could only scrape the rebound wide on the slide.
Janneh threatened again on 52, nodding into Hladky’s arms from an angle on the left, then a minute later shot well over having been found in space on the left of the box.
In the 55th minute, Town made a change, Luongo making way for Leon Ayinde, the Australian international having sat on the turf moments earlier indicating what’s hopefully a minor injury.
Ayinde, like Carr, was among the young players to join the club in January, in his case from Cork City.
As the game hit the hour mark, Ladapo saw a shot deflect wide, but with the U’s having been putting the Blues under pressure at the other end without managing a serious shot.
On 62, the home side swapped Harrison Dunk, danger man Janneh and Jubril Okedina for Liam Bennett, Danny Andrew and Fejiri Okenabirhie.
Soon after, Ahadme claimed he was fouled as he looked to get onto a cross from the right but in truth he had collided with Woolfenden as the pair both had their eyes on the ball.
In the 64th minute, with the U’s still on top against a very under par Town, Ahadme was sent away down the middle but Woolfenden got back to block the Moroccan’s shot.
Six minutes later, Town found themselves short on numbers as Cambridge broke and Okenabirhie struck a shot from the left which Hladky bundled away.
On 72, a neatly worked Blues move almost saw Chaplin played in on the right of the box but Stevens was off his line quickly to claim ahead of the forward.
The Blues made further changed in the 76th minute with Rio Morgan and Harry Barbrook taking over from Hutchinson, who showed more than enough to excite Town supporters on his first appearance, and Carr, who will have benefited from the experience.
Cambridge subsequently made three more substitutions, Lankester, Ahadme and James Brophy making way for Glenn McConnell, Kai Yearn and a trialist.
Town continued to huff and puff and on 86 Fin Barbrook took over from Davis, who had earlier required treatment for an ankle knock before continuing.
A minute later, Okenabirhie shot over from a tight angle on the left with the U’s having looked the more likely victors of the match for most of the second half.
And in the final minute, that winning goal came. A free-kick from the left wasn’t cleared and the ball fell to veteran Suffolk-born Cambridge skipper Michael Morrison, who slammed into the net.
Moments after the restart, the final whistle ended a rather disappointing display from the Blues with Cambridge deserved winners on the balance of the second half.
Town had started very strongly and having gone in front might have added to their lead via numerous chances.
But the U’s came more into the match, equalised and then never allowed the Blues to get back on top showing the sort of intensity which gave Town such a tough afternoon in League One in February, a game Kieran McKenna’s men were fortunate not to lose.
Harness might have given the Blues the lead again in the second half but most of the chances fell to the home side with Morrison taking his opportunity when it came in the final moments.
The Town management and fans now move on to Stevenage for this afternoon’s second game when boss Kieran McKenna will be looking for a better performance from his other XI.
Cambridge United: Stevens, Digby, Morrison, R Bennett, Brophy (Trialist 78), Thomas (Simper 72), Lankester (McConnell 78), Dunk (L Bennett 62), Okedina (Okenabirhie 62), Janneh (Andrew 62), Ahadme (Yearn 78). Unused: Holden, Sandiford, Hoddle.
Town: Hladky, Carr (H Barbrook 76), Woolfenden, Burgess, Davis (F Barbrook 86), Evans (c), Luongo (Ayinde 55), Hutchinson (Morgan 76), Chaplin, Harness, Ladapo. Unused: Hayes. Referee: (Leicestershire). Att: 2,936 (Town: 517).