Anuj Dal hit a maiden half-century but Derbyshire lost by 30 runs to Lancashire at Emirates Old Trafford in the Royal London One-Day Cup.
Mark Watt took 2-50 as five Derbyshire bowlers took a wicket in the first innings as Lancashire posted 239-6.
However, the hosts restricted Derbyshire to 209-7 despite a career-best effort from Dal (52) and a strong knock from Billy Godleman (42), after the match had been reduced to 38 overs per side due to rain.
Derbyshire got off to a strong start after winning the toss and electing to bowl, as Wayne Madsen had Haseeb Hameed stumped by Harvey Hosein without scoring in the first over.
Steven Croft then joined Keaton Jennings in the middle, as both batsmen looked to accelerate the run rate, however Rampaul took his first to remove the former for 18.
Jennings continued alongside Dane Vilas (25) as the pair added 52 for the third wicket before Luis Reece came into the attack to remove Vilas and break the partnership with his first ball.
England international Jennings then passed his half-century as he and Jake Lehmann put on an 86-run stand to take the score to 180-3.
However, Logan van Beek returned to remove Jennings (84) before Lehmann also brought up his fifty on debut for the hosts.
Left-arm spinner Mark Watt then took two wickets in quick succession to remove Rob Jones (9) and Josh Bohannon (6) to slow Lancashire’s late charge.
Lehmann continued his form to reach 77 not out at the innings close, as the hosts posted 239-6 from their 38 overs.
Openers Reece and Godleman made a strong start in reply as the pair both struck boundaries to take Derbyshire to 45-0 after eight overs.
Reece then fell for 19 as Lancashire adopted a pace-off approach with their bowling, with Madsen and Godleman watchful on a slow pitch.
Madsen (14) was then caught on the boundary as Jones took his first as the visitors slipped to 74-2.
Croft returned to the attack to take two wickets in an over, as Godleman (42) and Tom Lace (9) both fell in quick succession.
Wickets continued to fall at regular intervals as Alex Hughes (6) was run out by Jennings, before Matt Critchley (12) also fell to take the score to 122-5.
Dal and Harvey Hosein (41 not out) provided a late resistance as the pair put on a 76-run stand for the seventh wicket as the former brought up his first half-century for the club.
Dal then fell for 52 as Derbyshire closed on 209-7 and ultimately came up 31 runs short of the 240 target.
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