Bristol City secured a memorable comeback victory as Marco Silva's promising start to life at Watford came to a shuddering halt in the Carabao Cup.
Lee Johnson made nine changes at Vicarage Road with half an eye on Friday's Championship clash with Aston Villa, yet it was the unfancied Robins that emerged victorious at Vicarage Road.
Etienne Capoue put the Premier League side ahead early in the second half, only for 18-year-old Freddie Hinds to draw level in style before substitute Bobby Reid and Niclas Eliasson secured City a 3-2 second-round win at Watford.
It was quite the turn up for the books given Johnson's widespread alterations and Silva's bright start to life at Vicarage Road, with the home draw against Liverpool followed by victory at Bournemouth.
However, City rallied impressively after falling behind to Capoue's goal at the start of the second half and picked up a memorable win.
Hinds, Reid and Eliasson were the heroes for Johnson's men, with Watford's bad night compounded by Jose Holebas' late sending off before a later Adrian Mariappa consolation.
Silva made six alterations for the second-round tie but fielded a strong lineup, including handing summer signing Will Hughes his debut.
Given those changes and City's nine it was little surprise that the encounter got off to a disjointed start, with both teams struggling for coherence and a cutting edge in the final third.
Troy Deeney, making his first start of the campaign, was the focal point of the Hornets' attack but was unable to turn his side's best chances into a goal, nodding wide before being denied by a superb recovery tackle by Birmingham target Aden Flint.
The first half was a trying affair for those at sparsely-filled Vicarage Road, but the second half was far more open and entertaining.
Nice team interplay that belied anything witnessed in the opening period led to Hughes threading through Capoue, who showed good strength and composure to lash home.
Watford soon took their foot off the gas, though.
Hordur Magnusson saw a header deflected wide before Hinds took matters into his own hands, taking aim from distance with a fine shot that beat Heurelho Gomes in the 60th minute.
City were not done there. Just seven minutes later Lloyd Kelly's driven cross from the left was met in the box by substitute Reid, directing into the Watford goal from six yards to the delight of the visiting fans.
Richarlison saw a header come back off the foot of the post before Callum O'Dowda was denied as play swung from end to end, with substitute Andre Gray then thwarted by Frank Fielding.
However, Watford's night would soon get worse as Holebas received a second yellow card before Eliasson slotted home for City.
Mariappa scored a consolation goal but many of his fans had already headed to the exit.