Ben Slater hit 40 and Anuj Dal made his first-class debut, but Derbyshire lost to Sussex by 243 runs on the final day at Hove.
Chasing 405 runs to win, Derbyshire made 58 without loss, before the hosts began to take regular wickets and close in on victory.
Slater was ruled out of the remainder of the innings after being struck on the head on 40 and his concussion replacement Dal showed resistance in his 25 before Derbyshire were all out for 161.
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