Derbyshire 289 for 5 (Madsen 119*, Hughes 69) beat Warwickshire 288 for 7 (Thomson 68*, Mellor 58) by five wickets
An unbeaten 119 from Wayne Madsen steered Derbyshire to a five-wicket victory over Warwickshire to keep them on course for the knock-out stages of the Royal London One-Day Cup.
But Madsen was dominant and, although Thomson followed his unbeaten 68 with 3 for 57, Alex Hughes made 69 as Derbyshire won with 21 balls to spare to eliminate Warwickshire.
Warwickshire had to win to stay in contention but they were struggling when they lost three wickets for 15 runs to slump to 113 for 5 in the 22nd over.
Ed Pollock top-edged a return catch to Logan van Beek and Dominic Sibley edged the last ball of the first Powerplay before Luis Reece took the key wicket of Sam Hain.
Hain had scored an unbeaten 161 in the previous game and looked set for another significant innings until he tried to cut Reece and was caught behind for 34 in the 17th over.
With Watt's accurate and disciplined spell accounting for Will Rhodes and Liam Banks, the innings stalled until Thomson struck the first boundary for 10 overs.
He pulled Ravi Rampaul for a six and two fours in an over to give Warwickshire renewed momentum which increased when Mellor twice drove Critchley for six in an over which cost 19.
Mellor top-edged a pull but Thomson and George Panayi added 58 before Henry Brookes drove van Beek for six in the last over to give Warwickshire a challenging total.
Billy Godleman drove and cut Brookes for three consecutive fours but was bowled by Thomson for 40 and Reece was caught at slip when he cut the spinner onto the wicketkeeper's thigh.
Tom Lace miscued a pull at Jetan Patel's first ball but Warwickshire's bowling was too inconsistent to apply any sustained pressure and Madsen played with authority from the start.
He drove Patel for two consecutive fours to reach 50 from 43 balls and, with Hughes, took the game away from Warwickshire.
Hughes drove Thomson for six and repeated the shot in his next over before he drove Patel back over his head in the 33rd to take the target below a hundred.
Patel was Warwickshire's best hope but Madsen never allowed him to settle, driving him for six and the stand was worth 134 in 22 overs when Hughes was well caught at mid on off Thomson.
Madsen completed his fifth List A 100 from 92 balls and sealed Derbyshire's third victory with his fourth six in the 47th over.