David Ripley felt it was a 'tale of two powerplays' after the Steelbacks suffered a 12-run defeat to Durham Jets on Friday night.
Northants could not hunt down the Jets' 174 for seven at the County Ground, having got off to a sluggish start.
They were 37 for two at the end of the powerplay, with Ricardo Vasconcelos and Josh Cobb having departed.
At the same stage, Durham had been 59 for one, and Ripley feels the differing displays of the two sides in the opening six overs of the innings proved crucial.
"It was a very slovenly start from us," Ripley said.
"We drifted in, conceded nearly 60 off the first six overs on a pitch I thought had something in it.
"When we bowled a good length, it wasn't easy, and when they came out and bowled that same length, it wasn't easy.
"There was a 22-run difference in the powerplays and the final margin is less than that so we're disappointed with those two powerplays. It was a tale of two powerplays.
"But we fought back well, I still thought we'd win when they made that total, but it wasn't to be again."
Durham are now top of the Vitality Blast North Group, having won nine of their 12 games so far.
The Steelbacks stay bottom with just three points to their name, having lost 10 of their 12 matches, including all six of their home games.
And Ripley added: "We were quite some way below our best tonight.
"We haven't been good, week in, week out, we haven't been good in a whole game, but we were within a stone's throw of beating the team that is top of the league.
"The frustrating thing is that we were close but we weren't anywhere near our best."