MK Dons edged out a young Tottenham side 1-0 at Stadium MK on Wednesday thanks to a first-half Giorgio Rasulo goal.
A Spurs side made up largely of reserve players was missing star names like Gareth Bale and Jermain Defoe as the senior side prepare to face Monaco on Saturday.
Tottenham began well with Kevin Stewart heading down at goal from a corner, only for Ian McLoughlin to collect, before Chelsea loanee Patrick Bamford put a one-on-one effort wide for MK Dons after 12 minutes.
Ten minutes later, Cameron Lancaster wasted a good chance for the visitors, skying over from close range but eventually, after 34 minutes, the home side deservedly took the lead through Rasulo.
The 16-year-old took a through ball from Bamford well and, despite seeing his first effort saved by Jonathan Miles, he kept cool and dispatched the rebound to put MK Dons one up.
Shaquile Coulthirst should have made the scores level on the hour mark but failed to hit the target from the edge of the box, having been one-on-one with McLoughlin, something which Kelvin Osei-Addo almost punished him for five minutes later.
He was played in by Jon Otsemobor, but his effort was well saved by Jordan Archer before Tom Flanagan produced a goal-line header to keep the score at 1-0.
Tottenham piled on the pressure as the game approached full-time, with Kenny McEvoy having two good efforts on goal.
Coulthirst then hit the side netting with a minute remaining but the League One side held on to record a hard-fought victory.