Although in pain after being struck by a Simon Francis yorker, the England opener made 55 from 96 balls and took Lancashire to the brink of a comfortable victory over Hampshire Hawks with six wickets and 33 balls to spare.
It was the former England captain's third fifty in five League innings this season, and lifted Lancashire above Worcestershire Royals - who they play at New Road in the last match of the season a week on Sunday.
Hampshire won the toss and chose to bat but their middle order was wrecked by a superb spell by Andy Flintoff. Giles White and Robin Smith had put on 71 in 15 overs to take the Hawks to 85 for 2 when Flintoff bowled Smith for 36 in the 24th over. Four overs later the 21-year-old all-rounder had Will Kendall and Dimitri Mascarenhas caught behind with consecutive balls, and although Shaun Udal denied him a hat-trick, he was bowled two balls later.
He ended with figures of 4 for 24, his best in one-day cricket, and when White was run out after reaching a 68-ball 50, Hampshire had slipped to 109 for 7. Adrian Aymes and Simon Renshaw then led Hampshire to 180 for 8, putting on 69 for the eighth wicket, although Peter Martin returned to have Aymes caught to complete impressive figures of 2 for 22 in nine overs.
Flintoff then gave Lancashire's reply a flying start by hammering 27 off 27 balls with four fours and a six. He was bowled going down the pitch to Francis but John Crawley joined Atherton in a third-wicket stand of 50. After Crawley and Atherton both fell to Udal, Neil Fairbrother compiled an unbeaten 27, before Graham Lloyd sealed the win with a six.
n Michael Slater will not be returning to Derbyshire next season. The Australian joined the club in 1998 but scored only two first-class centuries in two seasons. Another Derbyshire batsman, Tim Tweats, is to retire from the first-class game.