Captain Josh Cobb was left with mixed feelings after his match-winning innings against Worcestershire Rapids.
Cobb smashed a superb 62 from just 32 balls, which included seven sixes, as the Steelbacks won by seven wickets in front of a big crowd at the County Ground.
But while Worcestershire can now look forward to a Vitality T20 Blast quarter-final, the Steelbacks have bowed out of the competition.
They only won four of their 14 North Group matches, losing six and having a further four matches abandoned due to the weather.
And Cobb said: "It's difficult to sum it up. We're obviously happy with our performance and to finish the competition on a high but at the same time it's frustrating knowing you can put a performance like that in against a high-quality side in the last game.
"Maybe we didn't put enough performances in like that early on in the comp and it meant we couldn't qualify. We've showed we're a dangerous side.
"It is frustrating but it's gone now and we can't qualify, it's finished.
"It's nice to take some momentum into next year and we've still got a good chance of getting promoted (in the County Championship).
"It's good for us ahead of the final three Champo games."
On his own performance against Worcestershire, Cobb said: "I've been pretty poor in this comp so it's nice to prove to myself I can still clear the ropes from time to time.
"It's nice to do it and great to get the win but on the other hand it's frustrating we've not played like that more times than not in the comp."