The Steelbacks came out on the wrong side of a County Ground runfest for the second time in three days as the Notts Outlaws earned a 58-run win on Friday night.
Ben Duckett, who made 96 in the four-wicket defeat to Leicestershire Foxes on Wednesday, again impressed for Northants, smashing a superb 88.
But he couldn't help his team get home as they were all out for 161, failing to chase down the Outlaws' incredible 219 for six, in which captain Dan Christian delivered a sensational unbeaten 113 from just 40 balls.
The Steelbacks had won the toss and elected to field, making early inroads as Notts slipped to 44 for three.
But Christian and Samit Patel produced a huge partnership to steer their team to a massive total, despite the efforts of Ben Sanderson (2-41), Rory Kleinveldt (2-53) and Seekkuge Prasanna, who took one for 21 from his four overs.
And though the Steelbacks started strongly - they were ahead of the Outlaws for long spells - the pressure eventually told as they suffered their second defeat in as many Vitality Blast matches this season.
The Steelbacks had hoped for some welcome relief after Leicestershire reached their victory target of 219 in Wednesday's tournament opener, and they got the early wicket of the dangerous Riki Wessels, who was bowled by Sanderson for just six.
Tom Moores was the next man in and he showed real intent before being trapped LBW by Kleinveldt for 15.
And the wickets were starting to tumble when Nathan Buck struck with his second delivery, having Steven Mullaney caught behind for 21.
At the end of the powerplay, Notts were just slowing down on 50 for three and although Patel and Billy Root helped them rebuild, the Steelbacks struck again before the halway point.
Steven Crook took a superb diving catch just in from the boundary to get rid of Root for 21, giving Prasanna a wicket that he celebrated in trademark fashion.
Patel should have gone soon after but a mix-up in the field between Kleinveldt and Richard Levi meant the ball dropped in between the South African pair to give the Outlaws a let-off.
Notts then started to make the Steelbacks pay with four sixes in just five balls as Patel and, in particular, captain Christian took a liking to the spin of Graeme White.
Patel and Christian were forming a prolific partnership, racking up their combined 50 in just 27 balls.
Christian brought up his own half-century in just 21 deliveries and set things up nicely for the final four overs as the Outlaws moved past the 150 mark, having lost just four wickets.
Eventually, the Steelbacks struck as Kleinveldt was brought back and he dismissed Patel for 35 thanks to a catch from Buck at short third man.
Sanderson bowled Paul Coughlin for four, but Christian continued in relentless fashion, reaching his century in just 37 balls.
He eventually finished unbeaten on 113 as the Steelbacks were set an eye-watering 220 to win.
But Duckett wasn't fazed as he took Patel to task in the third over, which cost the Outlaws a whopping 30 runs.
Levi again went cheaply though as he was caught by wicketkeeper Moores off the bowling of Luke Fletcher for three.
Duckett powered on though, reaching his half-century in an amazing 17 balls.
Josh Cobb couldn't provide much support as he holed out to Root off the bowling of Harry Gurney for six.
The Steelbacks ended the powerplay on 74 for two, with Ricardo Vasconcelos having played a couple of tidy shots to find the boundary.
Northants were 24 runs and one wicket better off than the Outlaws at the same stage, but Mullaney soon removed Vasconcelos for 10, with Christian taking the catch.
Alex Wakely looked in good touch early on but he was run out for 12 after thinking about a second run and turning back, only to find himself short as the ball hit the stumps.
The Steelbacks retained hope with Duckett still in the middle, but Mullaney eventually got rid of him for a fine 88.
That left the home side on 123 for five, needing another 97 runs for victory in just 7.2 overs.
And they were to lose two quick wickets from the final ball of the 15th over and the first ball of the 16th as Prasanna and Crook departed for 12 and 18 respectively.
Kleinveldt soon followed as Fletcher had him caught for one, leaving the Steelbacks on 156 for eight as the County Ground fell silent.
White went for five as Coughlin took a fine catch off Fletcher to leave the Outlaws needing just a single wicket for victory.
And they got it soon after as Gurney wrapped things up by bowling Buck for three.
Steelbacks: Levi, Duckett, Cobb, Wakely (c), Vasconcelos (wk), Crook, Kleinveldt, Prasanna, White, Buck, Sanderson.
Nottinghamshire Outlaws: Mullaney, Wessels, Moores (wk), Patel, Root, Christian (c), Fraine, Coughlin, Fletcher, Sodhi, Gurney.