Chapple’s Lightning failed to qualify out of the North Group for the second year running, having won the competition in 2015.
This summer’s campaign started so well with a win away at Durham on opening night, but things drifted badly to leave them needing to win their last two games last week and hope other results went their way.
They beat Worcestershire at Old Trafford on Wednesday before losing to Birmingham on Friday.
It meant they finished seventh in the group on 13 points with five wins, six defeats, a tie and two ‘no results’. They were four points behind Leicestershire in fourth.
Coach Chapple said: “Both groups have been the same. So many teams could qualify going into the last game. We lost in the last over on Friday and Notts too. It possibly could have changed.
“We’re looking for a campaign where we dominate.
“It started well and then got patchy. When you just go out, you can always point to areas which would have just got you through. What that doesn’t hide is the areas where we can improve.
“If you’re looking to qualify well, we haven’t played well enough. We have to admit that to ourselves.”
Chapple pointed to bowling early in the innings as one key area which let his side down.
“We’ve struggled to get through the power play,” he said. “Part of that is that we’ve struggled to find a balance.
“Matthew Parkinson has come in and been fantastic, and he’s a real positive for the future. But with that comes a challenge to balance the team.”
Lancashire return to County Championship action on Monday when they host bottom side Warwickshire.