Other news: Former director of cricket David Houghton returned as head of cricket in October, while MCC head coach Steve Kirby has joined as assistant and bowling coach. T20 bowling coach Dominic Cork has stepped up to take the head coach role in that format, replacing John Wright, who has taken on a new advisory role including recruitment and strategy. The county need a new T20 captain following Wilson's departure.
Overseas player 2018: Aiden Markram (South Africa), Tom Latham (New Zealand), Imran Tahir (South Africa), Axar Patel (India)
Other news: As well as replacing retired Championship skipper Collingwood, the county will need a new limited-overs captain if Latham does not return. Marcus North and James Franklin have replaced Geoff Cook and Jon Lewis as director of cricket and head coach respectively. Second XI and bowling coaches Neil Killeen and Alan Walker have swapped positions, while the county are looking to appoint a batting coach.
Overseas player 2018: Peter Siddle (Australia), Neil Wagner (New Zealand), Adam Zampa (Australia), Murali Vijay (India)
Possible signings: The county are "actively speaking" to one or two potential batting signings - and may need a replacement overseas player if Marsh makes Australia's Ashes squad.
Other news: Head coach Robert Croft left the club on 17 October. Ex-captain Mark Wallace returned as director of cricket in December, with Hugh Morris focusing on his role as chief executive after carrying out the dual role since 2013. Batting consultant Matthew Maynard has stepped up as interim head coach and will hold the role until the end of the season. The county will need a stand-in captain for the One-Day Cup after limited-overs captain Colin Ingram was signed for the Indian Premier League.
Overseas player 2018: Dan Worrall (Australia), Michael Klinger (Australia), Thisara Perera (Sri Lanka), Andrew Tye (Australia)
Other news: The county need a new T20 captain after Elliott's retirement. Batting coach Tony Frost has given up his second team responsibilities, with Ian Westwood stepping up from his position as development coach to take charge of the side.
Overseas player 2018: Travis Head (Australia), Callum Ferguson (Australia), Martin Guptill (New Zealand), Wayne Parnell (South Africa)