Northants threw away a golden chance of taking a massive step to securing a place in the quarter-finals as they were beaten by a Rapids side who already been eliminated from this season's competition.
And the Steelbacks, who have now lost three matches in a row, go into the final two games of the Central Group campaign knowing they are going to need at least one victory to extend their season beyond this weekend.
Chasing the visitors' 178 for six, the Steelbacks were in cruise control as they went into the seventh over of their innings sitting pretty on 73 for one, with Richard Levi smashing a 27-ball 50.
But skipper Josh Cobb's dismissal sparked a mini collapse that saw Northants falter badly as they were reduced to 90 for four at the 10-over mark.
And despite a 61-run partnership between Adam Rossington and Saif Zaib that saw the home side back in the game and needing 17 off the final 10 balls, they ran out of steam and luck and fell short at 170 for seven.
"It was a much better performance that the previous two matches," said Ripley.
"We bossed the powerplay and Richard Levi was outstanding up front and we were only one down, but then in the next three overs we lost three wickets and only mustered 19 runs.
"That meant that all of a sudden we were back behind where Worcester had been in their innings, and that was a really crucial part of the game.
"We neither did one thing or the other, we didn't save wickets or score runs at a good rate, and that became costly.
"We had to rebuild, because all of a sudden we could have been six down, so Adam did that and he was in at the end and almost got over the line with a hand from Saif Zaib.
"Take those four overs out of our innings it would have been a very good run chase, but we have ended up eight runs short and we should really breeze another eight runs, or have another two wickets up our sleeve so we could have gone earlier.
"It is frustrating to have got so close.
"At half-time I was reasonably happy we could chase that score down, and once you come out of the powerplay as we did we were well ahead of the game, and I think we should manage ourselves to victory from there.
"We played an extra batter and that should have got us over the line."
The Steelbacks now have two away games to finish the group.
They go to Somerset on Friday (5pm) and then Birmingham Bears on Sunday (1pm), and one win is likely to be enough to ensure the Steelbacks reach the last eight, but that is not guaranteed, as it would still depend on other results.