Worcestershire 209 for 4 (Whiteley 84*) beat Derbyshire 181 for 7 (Madsen 40) by 28 runs
Ross Whiteley hammered an unbeaten 84 against his former county to help Worcestershire secure a NatWest T20 Blast quarter-final place by beating Derbyshire by 28 runs at New Road.
Worcestershire roared to victory after man-of-the-match Whiteley slammed nine sixes and two fours off 38 balls. Victory enabled skipper Daryl Mitchell's men to march into the last eight for the second time in three seasons, with a trip to Surrey awaiting them.
Derbyshire finished firmly anchored at the foot of the North Division with only one win throughout their entire campaign, which ended with six losses on the trot.
Worcestershire, who completed the double over Derbyshire after winning by eight runs under the floodlights at Derby last month, were put in after losing the toss and made 209 for 4.
They got off to a solid start, with Mitchell signalling his intention by collecting a confidently struck boundary off the first ball of the innings. He put on 38 in four overs with fellow opener Richard Oliver, who then sliced Greg Cork to Matt Higginbottom at cover.
After smacking six fours off 19 balls, Mitchell pulled Ben Cotton to Wayne Madsen to depart for 36 before Tom Kohler-Cadmore and Colin Munro brought up the 50 off the first ball of the sixth over.
They were 64 for 2 at the end of the six-over Powerplay but Munro's hopes of a big innings, after cracking three successive fours, evaporated when he was bowled for 16 attempting to reverse-sweep Marcus North.
Whiteley was dropped by Alex Hughes off Wes Durston on 25, though the next delivery saw Hughes redeem himself by holding on to a catch at long-on to remove Kohler-Cadmore for 22.
Whiteley made the most of his let-off by reaching a half-century off 28 balls, with five sixes and one four. He needed only another 10 balls, featuring four sixes and a four, as he made his highest score in all cricket for Worcestershire and put on 89 in 7.4 overs with Ben Cox, who made 29 not out.
In reply, Derbyshire lost North to New Zealand paceman Mitchell McClenaghan before they completed their Powerplay on 57 for 1. Gareth Cross and Wes Durston produced bright and breezy knocks of 34 and 36 respectively, but Worcestershire battled hard to keep them in check with some smart fielding and bowling.
Billy Godleman and Madsen gave their side hope with a stand worth 56 in 4.2 overs, but once the fourth-wicket partnership was broken by Jack Shantry, Worcestershire went on to wrap up their eighth win of the season by restricting the visitors to 181 for 7, Madsen top-scoring with 40.
Worcestershire's chief executive David Leatherdale was delighted by the club's progress to the quarter-finals. "T20 has been good us," he said. "We started with two losses on the road and then got six wins in a row to give us the momentum. We've played some decent cricket and everybody has dovetailed at some point to get us to this position.
"To progress to the quarter-final in what is a tough group, when you've got Lancashire, Notts, Durham and Yorkshire, we certainly probably wouldn't have been top of the list to qualify at the start of the season."
Derbyshire's elite performance director Graeme Welch praised his side's work ethic despite their poor record in the competition this season: "We didn't win any games in anything early season and that dragged us down, but the lads have been brilliant and kept going all the time.
"The work ethic has been second to none and they have kept doing all we have asked of them, but it's been difficult."