It was a second time in the space of 24 hours that the Northants attack had failed to defend a sizeable total, with the Bears chasing down the home side's 211 for six with six wickets and seven balls to spare.
That followed on from Derbyshire cruising past the Steelbacks' 186 for seven with an over in the bank the previous evening, and it means John Sadler's team still have a lot of work to do in their final two group games to secure a top four finish.
A win over the Bears would have seen them go top, but instead they drop to fourth, just two points ahead of fifth-placed Leicestershire Foxes and three clear of sixth-placed Yorkshire Vikings, who have two games in hand and visit the County Ground on Friday night.
It was the Steelbacks’ first home defeat of the campaign.
"We were very pleased with the score, but we knew it was a good wicket and that they have a dangerous batting line-up," said Cobb.
"We knew they would come hard and we would be under the pump at some stage, and we picked up early wickets although the run-rate was there.
"We were probably just one or two wickets away from really being ahead of the game, but they kept coming hard and they played very well."
There were half-centuries for Adam Hose and Chris Benjamin, the pair putting on an unbroken stand of 100 to see their side home.
Aside from Ben Sanderson, who claimed two for 18 in his three overs, the Northants bowlers struggled, with left-arm wrist spinner Freddie Heldreich going for 59 from four and Tom Taylor 50 from four.
"Our execution could have been better on the day," admitted Cobb, who surprisingly failed to bowl when he normally opens the bowling with his off-spin.
"We were slightly off from where we have been, but we have been playing some good cricket and we now obviously have two big games to come.
"We have to now get back on the horse and go again, we need to get some wins back under our belts."
With the bat, Saif Zaib top-scored for the second match in a row, hitting 74 from just 32 balls while run machine Chris Lynn chipped in with 59 from 43, but their efforts weren’t enough.
Bears skipper Carlos Brathwaite was delighted with his team's batting performance, although he wasn't quite so happy with the bowling and fielding.
"We didn't think it was going to be as easy as it was in the end," admitted the West Indian.
"We had a chat and we know that wasn't our best bowling performance, but we had a chance to make amends with the bat.
"We have been batting well all season, and I think that is probably our fifth or sixth 200-plus score, so we didn't think it was out of reach.
"But the way that the boys went out and played it was exciting to watch."
And he added: "We talk about staying positive and taking the game on, and taking the initiative as a batter.
"In past games we have been rolled and were a bit reckless, so I want them to be positive, be expressive but be a bit smarter.
"There were a few balls in certain situations where we as management could see that the guys, although taking the game on, took the smart option as well."