An extra-time goal gave Arsenal a 1-0 victory and sent Chelsea out of the Under-21 Premier League Cup.
The quarter-final exit at Aldershot’s Recreation Ground was the young Blues’ first defeat in 15 matches and came despite them being on top for much of the game.
Lewis Baker, Jeremie Boga and Isaiah Brown brought saves from Gunners keeper Matthew Macey, while Alex Davey and Alex Kiwomya also had chances for Dermot Drummy’s side but were unable to hit the target.
Arsenal should have scored an injury-time winner, but midfielder Jon Toral missed a golden chance when he sliced wide of an open goal after being set up by Thomas Eisfeld.
The first period of extra time also failed to produce a goal, with Baker hitting the bar and Nathan Ake saving Chelsea by clearing off the line from Eisfield.
But the deadlock was broken 19 seconds after the restart when Benik Afobe latched onto a long ball and chipped keeper Mitchell Beeney.
Andreas Christensen’s header wide from Baker’s free-kick was the closest Chelsea game to an equaliser.