Derby confirmed a third place finish in the Sky Bet Championship with one game to spare by putting four past Watford in a chaotic Sky Bet Championship clash.
Goals from Craig Forsyth, Chris Martin and a Jeff Hendrick double cancelled out an early Troy Deeney strike and a Mathias Ranegie header, to pick up a well-deserved win.
The Derby players were unlucky not to have been in front at half-time after dominating the play for long periods of the opening 45 minutes.
A great ball from Cristian Battocchio sent Deeney clear to give Watford the lead after just five minutes, who fired into the roof of the net past Derby goalkeeper Lee Grant.
But from thereon in, Derby took the half by the scruff of the neck.
Myriad chances were spurned by the Rams before a poor Daniel Pudil clearance allowed Hendrick to take a touch and put away his second goal in as many games just before the half-hour mark.
The Rams had opportunities to turn the game around before half-time, most notably through Jamie Ward, who was running the Hornets’ backline ragged, but the visitors held out to end the opening period with nothing between the sides.
An eventful second period burst into life with Forsyth putting the Rams in front ten minutes after the restart, lashing the ball into the roof net from close range, and when Marco Cassetti was sent off moments later, things were looking rosy for Derby.
But Watford had other ideas and when substitute Ikechi Anya broke quickly, his cross from the right was headed home by Mathias Ranegie.
Derby weren't to be denied the win, though, and they soon begun to make the most of their extra man, passing well and stretching the visitor's back four, leading to late goals from Hendrick and Martin, which handed the Rams’ maximum points.
The visitors got off to a dream start when a defence-splitting Battocchio pass sent Deeney clean through on goal and the striker placed the ball high into the centre of Grant’s goal to open the scoring.
From the restart, Derby looked to draw level immediately, and won a corner from which Ward and Johnny Russell both had shots blocked as Watford put their bodies on the line to keep their lead intact.
Derby came within inches from an equaliser moments later, as Ward nutmegged Joel Ekstrand and played a teasing low ball across the six yard box, which was just beyond the outstretched leg of Russell.
The Rams came close to levelling again when a pass across the area was almost turned in by Ward, but it trickled agonisingly wide of Jonathan Bond's goal.
Derby were looking the most likely to grab the next goal and another opportunity fell the way of Bryson after a neat one-two with George Thorne, but the Scotsman’s powerful shot was deflected wide.
But the Rams wouldn't have long to wait for that elusive equaliser, when in the 28th minute, Daniel Pudil failed to get any power behind a headed clearance and Hendrick chested the loose ball down before slamming it past Bond to make it 1-1.
And the hosts could have taken the lead minutes later when Thorne picked out Ward in acres of space, but his shot was straight at the Watford ‘keeper who made a routine save.
Ward was posing a constant threat to Watford’s back four and after beating several defenders, the tricky forward must have been frustrated to see his curling effort drift just outside the right post.
The second period started slowly and it wasn't until around ten minutes into the half that the first chance was created.
Watford’s Pudil put in a low cross and Richard Keogh slipped in his attempt to block the pass, but Jake Buxton did well to nip in and clear the danger with Deeney breathing down his neck.
But just a few minutes later, Derby broke and finally got the second goal that their dominance had merited.
Russell picked up the ball deep in Watford’s half, held it up well and found Bryson, who laid it off to Forsyth and the left-back thumped a piledriver into the roof of Bond’s net to give the Rams the lead.
That goal seemed to spark the Rams into life and they began to boss the second-half in much the same way as they had before the break.
Martin could have scored when he stole the ball off the toe of a Watford defender, but Bond did well to save his close range effort.
And Derby’s top scorer had another chance moments later when he was found on the edge of the box and took aim, but his shot flew well wide.
As Derby were building pressure once more, Cassetti brought down Craig Bryson to earn his second yellow and an early bath, giving Derby a great chance to take control of the tie.
But it was Watford who would strike next, when the visitors broke down the right wing, and Anya’s whipped cross was met by Ranegie who headed home from six yards to equalise against the run of play.
The Rams looked to make amends immediately and some poor defending gifted Ward a chance to restore their lead, but his effort was blasted straight at Bond who beat it away without moving.
Simon Dawkins had been on the pitch only a matter of minutes when the ball was rolled to him 20 yards from goal, but his effort lacked direction and flew well wide.
Derby had struggled to make their extra man count, but with ten minutes to go, Hendrick scored his second of the game to put the Rams back in front, with a fantastic strike from outside the box, making it 3-2.
And just five minutes later, Martin made things comfortable for the home side as he slid the ball past Bond and into the bottom right corner to make it 4-2 to the hosts.
Bryson could have made it five in stoppage time as he burst into the Hornets’ box, but when he shot, Bond dived low to his right make a good save.
Derby County: Grant (GK), Wisdom, Keogh, Buxton, Forsyth; Thorne, Bryson, Hendrick; Ward (Dawkins 74'), Russell (Bamford 75'), Martin (Hughes 87').
Subs not used: Legzdins (GK), Naylor, Eustace, Whitbread.
Watford: Bond (GK); Doyley, Cassetti, Ekstrand (Hoban 53'), Riera, McGugan (Anya 57') , Tozser, Battocchio, Pudil; Deeney, Ranegie (Faraoni 75').
Subs not used: Woods (GK), Merkel, Murray, Jakubiak.