Nottinghamshire bowler Luke Fletcher is given the all-clear to return to training in January following a head injury.
Ben Stokes is named in England's ODI squad to play Australia but appears unlikely to play while investigations into an incident outside a nightclub continue.
County champions Essex begin the defence of their title in 2018 against Yorkshire at Headingley on 13 April.
In a repeat of the 2017 final, holders Notts Outlaws will host Birmingham Bears on day one of next summer's T20 Blast.
Audio & Video
Notts captain Dan Christian gets more than he bargains for as he receives the T20 Blast trophy, the Australian gets hit in the face as the prize is hurriedly handed over.
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