Derbyshire 312 for 9 ( Reece 136, Pennington 3-59, Finch 3-54) beat Worcestershire 265 (Libby 126*, Conners 3-37) by 47 runs
The Derbyshire opener surpassed his previous best total of 128 – also against Worcestershire at Derby three years ago – in a perfectly paced innings which helped his side amass 312-9 on a hybrid pitch.
He was given excellent support by Shan Masood and Anuj Dal in stands of 137 and 91 respectively.
The Peakites will probably have to win their final three games to have a realistic chance of progressing through to the next round.
But Worcestershire remained rooted in bottom spot after a fifth successive setback in what has been a miserable summer of white ball cricket for the Rapids after picking up the wooden spoon in the Vitality Blast North Group.
Hundreds of spectators took advantage of Worcestershire giving away tickets, to families affected by Storm Dennis 2020.
Libby, elected to bowl first and Ben Gibbon was rewarded for a tight opening spell when Harry Came was caught behind after an expansive drive.
Masood joined Reece and instantly got off the mark by leg glancing Gibbon to four to set the tone for his innings.
Reece had played himself in before ramping Gibbon for six in the final over of the initial powerplay and the second wicket pair gradually flourished.
A straight drive for four by Reece off Dillon Pennington enabled him to complete 5,000 runs in all cricket for Derbyshire.
Reece completed an 82-ball half century with Masood needing only 46 deliveries to bring up his fifty.
Derbyshire raced onto 163-1 in the 31st over before Adam Finch, the pick of the Worcestershire attack, struck twice in the space of three balls.
Masood, on 63, was undone by a ball which bounced on him and edged through to keeper Ben Cox and Brooke Guest hooked his second delivery straight to Gibbon at deep square leg.
Reece needed only a further 45 balls to move to three figures and he accelerated even further during the initial stages of the final 10 overs.
Successive overs from Libby and Gibbon both yielded 20 runs before Reece’s excellent knock ended tamely on 136 when he struck a Taylor Cornall
full toss straight to long off. His 142-ball innings contained three sixes and 15 fours. There was a further success for Cornall when Dal, having raced to 46 off 34 deliveries, picked out Ed Barnard at deep cover.
Worcestershire collected a flurry of wickets in the closing stages of the innings. Mattie McKiernan (16) sliced Pennington to third man and the pace bowler accounted for Ben Aitchison and debutant Archie Harrison in his final over while Alex Hughes was bowled by Finch.
Conners immediately had Worcestershire on the back foot with a three wicket burst with the new ball. Cornall was strangled down the leg side and Ed Pollock, recalled to the side in place of the injured Kashif Ali, drove to mid off. Azhar Ali gave keeper Guest a second catch off Conners at 35-3 in the ninth over.
Reece came into the attack and struck in successive overs with Ed Barnard also nicking through to Guest and Ben Cox (12) bowled through the gate.
Libby batted with plenty of fluency and reached an excellent half century off 52 balls with six boundaries. Henry Cullen chopped on when Aitchison returned to the attack, Joe Leach swung across the line to Dal and was lbw and Pennington (35) was bowled by McKiernan.
Libby went past his previous List A best of 76 against Durham at New Road last summer before reaching three figures off 115 balls with one six and eight fours. Potts accounted for Finch and Gibbon to round off the innings and leave Libby unbeaten on 126.