Wimbledon produced a spirited second-half comeback after a lacklustre first-half but were unable to prevent a 2-1 loss to Brighton under-23s as they exited the EFL Trophy.
The Dons started poorly and left themselves with it all to do after going in at the break 2-0 down.
But a goal from Tyrone Barnett in the 67th minute gave them hope of taking the tie to penalties.
Tom Elliott, Tom Beere and Barnett all missed good chances to equalise in the closing stages as the game slipped away.
A tidy finish from Elvis Manu and a calm penalty from Richie Towell did the damage for Brighton as they scored twice in the last 10 minutes of the first-half.
The Seasiders also had keeper Niki Maenpaa to thank for maintaining their advantage as the stopper made three excellent saves to deny Dom Poleon, Jake Reeves and Barnett respectively.
Substitute striker Kazenga LuaLua made a lively second-half cameo for Brighton. He hit one fierce shot wide and another over the bar before getting sent off for four and abusive language to the linesman shortly before the end.