Blues, who will also face AFC Wimbledon, Leyton Orient and Milton Keynes Dons in the group stages of a competition they won in 2016 and 2018, fell behind to an early Andy Dallas goal before two efforts from former Southend loanee Jabo Ibehre rendered Matt Rush’s stoppage time finish to be a mere consolation.

The visitors started the game at a rainy Abbey Stadium on the front foot and had the first opening when Jon Benton’s tame shot was saved by Callum Burton in the Cambridge goal. A minute later the game was held up while Tom Knowles received treatment following a challenge by Benton.

That delay did not derail the hosts, and Cambridge took the lead on eight minutes as experienced striker Ibehre crossed for Dallas to score despite the best efforts of Harry Seaden and Miles Mitchell-Nelson, who desperately tried to clear the ball off the line.

Three minutes later a chance fell to Isaac Hutchinson but his shot was blocked by Harry Darling, and midfielder Benton then appeared to be bundled over in the box but appeals for a penalty were waved away.

On twelve minutes Cambridge rocked the Southend bar thanks to an Ibehre header following a great cross by Jordan Norville-Williams, and seven minutes later there was a great save from Seaden to deny Ben Worman at the expense of a corner.

Blues immediately broke downfield and Eren Kinali had a shot fielded by Callum Burton. Kinali was then involved in the action again when played through by Isaac Hutchinson, who is suspended for the EFL Trophy tie against Brighton & Hove Albion U21s, but Burton was again equal to the shot.

Midway through the first half Blues were opened up down the left and Mitchell-Nelson failed to deal with a cross but somehow Ibehre managed to direct the ball over the bar from very close range. The rain eased up a little and on 31 minutes Jon Benton embarked on an excellent break down the right and his cross found Hutchinson, whose powerful strike was well saved by Burton.

On 34 minutes trialist Henry Burnett gave the ball away in a dangerous position but was grateful to Seaden, who made a great save from Andy Dallas’ powerful shot. In an open spell of play a minute later the action was down the other end when Kinali had a chance to score but shot over the crossbar.

Six minutes before half-time Southend had their best chance of the half when Rush made a fantastic run, only for his shot to be tipped over by Burton. However, on 42 minutes there was a let-off for Blues from a corner when Seaden failed to collect the ball though a ruck of players and Tom Dickens’ shot was somehow scrambled clear of the danger.

Disappointingly for Southend the hosts doubled their lead on the stroke of half-time following a foul on the edge of the box by O’Shane Stewart. Tom Knowles fizzed in the free kick and Ibehre’s left-footed drive beat Seaden to his left and make it 2-0.

At half-time Blues withdrew Kinali for Zak Pianim. Pianim dropped in to right-back and skipper Rob Howard moved to wide midfield. Unfortunately the rain and thunder returned and the game became bogged down in midfield.

Blues made another change ten minutes in when Harry Phillips replaced Stewart. A minute later Blues had a great chance when Benton fashioned a goalscoring opportunity but his shot pinged back off the left-hand post to safety with Burton well beaten in the Cambridge goal.

U’s winger Jordan Norvelle-Williams was then booked for simulation when fairly challenged by Pianim in the Blues penalty area, and the visitors started to turn up the pressure. Louis John kicked the ball away to prevent a quick free-kick being taken and was cautioned before Tom Clifford’s set-piece in the 65th minute sailed disappointingly high of the target.

On 74 minutes Blues made a change bringing on first-year scholar Bobby Unwin for Tom Clifford. Four minutes later the hosts could have gone 3-0 up following a pacey break from Dallas after Rush lost possession for the Blues. The Cambridge striker powered a shot towards goal but Seaden made a great one handed save low to his left.

With seven minutes remaining the U’s did extend their advantage. There was an almighty scramble in the Blues box and Ibehre managed to turn the ball home with both him and Harry Seaden injured in the process and having to come off. With no substitute goalkeeper on the bench Sam Knock went in goal whilst youth team captain Sam Brogan also came on for Burnett.

Southend did manage to pull one goal back three minutes into injury time. Having been awarded a free-kick on the right-hand side of the Cambridge penalty area, the hosts failed to deal with the delivery and Rush was on hand to reduce the arrears.

Southend United U23s: Harry Seaden (Sam Knock, 84), Rob Howard, Tom Clifford (Bobby Unwin, 74), O’Shane Stewart (Harry Phillips, 55), Ide Osimeh, Miles Mitchell-Nelson, Jon Benton, Henry Burnett (Sam Brogan, 83), Isaac Hutchinson, Matt Rush, Eren Kinali (Zak Pianim, 46).