The defender's high ball was volleyed home by Joe Mills as Town took a 13th minute lead. However, Regan Poole levelled for The Dons late on in the half. Luka didn't come back out for the second-half, Keith Curle later confirming this was due to injury, as MK netted twice through Sam Nombe and Matthew Sorinola to take the win.
The Cobblers begin their Sky Bet League One campaign with a game against Jaakko Oksanen and AFC Wimbledon at Sixfields on Saturday.
Tonight could see Patrik Gunnarsson make his Viborg FF debut as they entertain Hobro IK in the NordicBet Liga while Julian Jeanvier and Kasimpasa are in Super Lig action on Sunday at Kayserispor.