Jamie Dalrymple and Ben Wright guided Glamorgan to a rare 50-over victory at Cardiff to put paid to any faint hopes Derbyshire had of reaching the Friends Provident Trophy quarter-finals.
After Derbyshire had been bowled out for 211, Dalrymple and Wright rescued the hosts from 66 for four in the 18th over with a stand of 135 - a record fifth-wicket partnership for Glamorgan in the competition.
Wright was out just before the end for 65, but skipper Dalrymple saw his side to a five-wicket win with 78 not out from 111 balls.
Derbyshire had gone into the game needing a convincing victory to have any chance of progressing to the last-eight, but after losing the toss they could not build on a solid platform.
They had reached 114 for one in the 29th over but some accurate Glamorgan bowling on a helpful pitch saw the visitors’ innings stutter and fall away.
In the end Derbyshire lost their final six wickets for the addition of just 50 runs.

Jamie Dalrymple led from the front for Glamorgan with a fine unbeaten 78 as they defeated Derbyshire by five wickets
After a first-wicket stand of 60, seamer Huw Waters grabbed the breakthrough when Greg Smith top-edged a catch to third man.
Fellow Derbyshire opener Chris Rogers went on to reach 50 from 71 balls but was undone by spin when he was bowled by Dalrymple for 59.
Three overs later former West Indies batsman Wavell Hinds was smartly stumped by Mark Wallace as he advanced down the wicket to slow left-armer Dean Cosker.
Cosker played a part in the next wicket as he caught Stuart Law at square leg off the bowling of Michael O'Shea and Garry Park went soon after when he edged James Harris to wicketkeeper Mark Wallace.
After one or two big blows Graham Wagg had his off stump removed by David Harrison, who two balls later had Dan Redfern caught behind.
Harris then bowled Tim Groenewald, and Jamie Pipe and Mark Lawson were both run out as Derbyshire’s innings came to an end with five balls of the final over remaining.
Glamorgan’s reply stuttered at the start as Mark Cosgrove was caught at cover from a Wagg slower ball to leave the score on 15 for one in the third over.
The Welsh county found themselves in further trouble following the dismissals of Michael Powell, O’Shea and Tom Maynard, but Wright and Dalrymple rebuilt the innings with some good running between the wicket.
After 42 overs Glamorgan took the batting power play with 36 arriving from the first four overs, and despite Wright going caught behind off Smith, Glamorgan went on to win with 16 balls to spare.
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