The County Championship will see three teams promoted and one relegated next year to create a 10-team top tier from 2020.
Derbyshire appoint MCC head coach Steve Kirby as the county's new assistant and bowling coach.
Derbyshire all-rounder Alex Hughes signs a one-year extension to his deal, keeping him at the club until the end of 2021.
Derbyshire wicketkeeper-batsman Harvey Hosein signs a new two-year deal, keeping him at the club until the end of 2020.
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