Watford crashed to their first defeat of the season as League One MK Dons booked their place in the Carabao Cup third round after a deserved 2-0 victory at Vicarage Road.
Matthew Dennis put the visitors ahead seconds before the break and there was no way back for Watford after Darragh Burns added the second in the 53rd minute.
The Dons looked nothing like League One strugglers early on as 19-year-old Louie Barry, on loan from Aston Villa, broke through on the left and almost squeezed a low shot past home keeper Maduka Okoye at the near post.
And there was another scare for Watford in the 19th minute when Will Grigg turned Craig Cathcart only for debut keeper Okoye to save at the striker’s feet.
Soon after, Dawson Devoy tried his luck, forcing Okoye into a diving save.
Watford, second in the Championship, finally came to life on the half-hour when a defensive mix-up left Vakoun Bayo unmarked in the six-yard box. Keeper Jamie Cumming held his shot at the second attempt.
But the Dons grabbed the lead seconds before the break. Sub striker Dennis, on for Will Grigg, won possession from William Troost-Ekong, fed Burns on the left and met the cross to score – colliding with the far post as he did so.
The visitors went 2-0 up in the 53rd minute when Devoy robbed Dan Gosling and set up Burns for a 20-yard left-footer past Okoye.
