Northants' NatWest T20 Blast title defence got off to a disappointing start as Derbyshire won by seven wickets at the County Ground.
The Falcons cruised to victory, with Northants suffering at the hands of Luis Reece, who racked up an unbeaten 75.
Wayne Madsen also chipped in with a valuable 37 as the away side claimed a rare win against their hosts.
Northants, whose star man was opener Ben Duckett, with 69, were made to pay for a mid-innings malaise, which was sparked by the loss of Josh Cobb for 38.
Alex Wakely went next ball and though Steven Crook provided an impressive cameo of 34 from 17 balls, Derbyshire knew they were in with a chance.
The Falcons overcame the loss of an early wicket and Reece showed composure as he saw his side home to leave Northants needing a response at Durham on Sunday.
Having lost the toss, Northants got off to the worst possible start as a mix-up between Duckett and Adam Rossington saw the latter run out for just five.
But that brought last year's final hero Cobb to the middle and the Steelbacks started to put pressure on Derbyshire.
Duckett was playing beautifully, timing a couple of fours and keeping the run rate high, with Cobb also looking sharp with some boundaries of his own.
The Steelbacks reached the six-over stage on 52 for one, forcing the Falcons to bring South Africa spinner Imran Tahir into the action.
Tahir steadied the ship slightly as he tried to force errors from the previously serene Steelbacks duo.
But Northants continued to plough on in the humid conditions at the County Ground, with Cobb smashing the game's first six.
Duckett made it to his half-century from 34 balls, but Derbyshire finally found a way through to end a 93-run partnership as Cobb was caught off the bowling of Hardus Viljoen for 38.
Steelbacks skipper Wakely went for a duck from the next ball, with Viljoen suddenly chasing a hat-trick.
But Northants stopped the Falcons bowler from getting it and Duckett was now the key as he continued to rack up the runs.
Rob Keogh got in the groove with a lovely six, but he was bowled by Tahir for 17 as the Steelbacks lost their fourth wicket of the innings.
Steven Crook was next to join Duckett in the middle, but Duckett, who had made 69, wasn't around for much longer as he was caught off the bowling of Matt Henry.
It was a big blow for the Steelbacks, who now needed big contributions from Crook and Rory Kleinveldt.
Crook had been searching for early-season form, but he is always confident in the T20 arena and he announced himself with three lovely fours as Northants took 16 runs from the 18th over.
Crook smashed a six in the penultimate over as the runs continued to pour for the Steelbacks.
And after Viljoen bowled a no ball to present Northants with a free hit, Crook cashed in again with a four.
Kleinveldt was caught in the deep from the penultimate ball of the innings, but Crook added another two runs from the final delivery, meaning the Falcons were set a victory target of 180.
Ben Slater got Derbyshire off to a decent start with two fours from the first over, but he nicked behind off Richard Gleeson to go for eight.
However, just as Northants had after the early loss of Rossington, Derbyshire rebuilt well, with Reece playing particularly well.
But opener Billy Godleman was stumped off the bowling of Cobb for 25, helping the Steelbacks to get back in the game.
Tabraiz Shamsi, the South Africa spinner making his Steelbacks debut, tightened things up after his first over had proved expensive, but Derbyshire were still just about on track.
The Falcons were 85 for two at the halfway stage and they really started to cruise soon after, with Reece and Wayne Madsen not giving the Steelbacks a sniff.
By the time Madsen went for 37, skying the ball to Rossington off the bowling of Kleinveldt, Derbyshire were in complete control.
And Reece carried them to a comfortable victory, alongside captain Gary Wilson.
Steelbacks: Duckett, Rossington (wk), Cobb, Wakely (c), Keogh, Crook, Kleinveldt, White, Sanderson, Shamsi, Gleeson.
Derbyshire Falcons: Slater, Godleman, Reece, Madsen, Wilson (c), Smit (wk), Critchley, Hughes, Henry, Viljoen, Tahir.