It is (almost) open season on county players. From June 1, any player out of contract at the end of the season can be contacted by other counties. In the past, a club wanting to make such an approach had to notify the contract-holding county 28 days before making any approach. But these days, they can go straight to the player, or their representative, and need only notify the contract-holding county of their interest.
Here we look at a selection of those whose futures are unclear or who are likely to attract the interest of other counties:
Henry Brookes (Warwickshire) Generally considered the most talented bowling prospect produced by Warwickshire since Chris Woakes, Brookes can bowl fast, is decent with the bat and appears to enjoy performing under pressure. Warwickshire will, no doubt, want to keep him. But he is currently unable to win a place in the side and is likely to have admirers elsewhere. Ed Pollock, who currently has the second highest strike rate of any man to have played a minimum of 20 T20s, is also out of contract.
Jack Brooks (Somerset) Brooks will be 37 in the first week of June and currently finds himself playing 2nd XI cricket. For a seam bowler, that feels like an uncomfortable place to be. But Brooks underwent operations on both Achilles tendons at the end of last season and, having had a late start to his professional career, feels there is plenty of petrol left in the tank.
Michael Burgess (Warwickshire) With no other keeper on the senior staff, Warwickshire have put a lot of faith in Burgess. He is starting to repay it, too, with some good work behind the stumps and an eye-catching century against Worcestershire. But that was his only time he had reached 40 against county opposition in any format of the game since the end of 2019 leading the club to start to consider contingency options.
Alastair Cook (Essex) At this stage of his career, Cook is content to play to the end of the season and decide if he wants to continue. It would be a major surprise if he could be lured elsewhere. Much the same could be said about Ryan ten Doeschate, who will be 41 in June and likely to make his own mind up about his future. Both are out of contract, though, so in theory approaches can be made.
Stevie Eskinazi (Middlesex) Eskinazi was Middlesex's captain in 2020 and at the start of 2021. But he hasn't made a first-class century against county opposition since 2017, and is playing second team cricket at present. He is understood to have been offered a new deal by Middlesex but is currently looking for a loan deal elsewhere. Nick Gubbins, Nathan Sowter, James Harris and Tim Murtagh are also out of contract at the club; all have been offered new deals.
Steven Finn (Middlesex) Finances at Middlesex are likely to be strained in the coming months. As if the absence of full houses for the start of the T20 campaign is not serious enough, the club also needs to find the funds to make good pension contributions that were not paid previously due to an administrative error. As a result, there may not be the funds for as many new contracts. Middlesex are understood to have offered Finn and John Simpson new deals but both are likely to have options elsewhere.
Richard Gleeson (Lancashire) Just a year ago, Gleeson was on the fringes of the England limited-overs team. But, having subsequently suffered a stress fracture, he hasn't played a first team game for Lancashire since August 2020 (and he has only played one for them since 2019). Now aged 33, he may require a good white-ball season to win another deal.
Dan Lawrence (Essex) With the club currently missing a chief executive, issues such as contract renewals appear to have fallen a little behind schedule. As with Cook and ten Doeschate, it would be a surprise if Lawrence could be tempted elsewhere but he is out of contract. The allrounder Paul Walter is also out of contract at the club.
Alex Milton (Worcestershire) Capable of playing as a keeper or specialist batter, Milton made an outstanding start to his career at Worcestershire with a century on Championship debut. But he struggled to sustain that level - he has been dismissed for a duck in four of his six most recent first-class innings - and finds his opportunities blocked by the presence of Ben Cox.
Tom Moores (Nottinghamshire) An interesting one this: Moores recently won his Nottinghamshire cap and his dad, Peter, is the side's head coach. So it would be a surprise if he left. He remains out of contract, though, and with his skills - not least his explosive white-ball batting - he is likely to have other offers. Luke Fletcher is also out of contract at Nottinghamshire.
Liam Plunkett (Surrey) Now aged 36, Plunkett has struggled with injury in recent months. He could yet play a prominent role in Surrey's limited-overs season but he is currently without a deal beyond October. Rikki Clarke, who will be 40 in September, is also out of contract at Surrey.
Darren Stevens (Kent) He may be 45, but Stevens is currently Kent's highest run-scorer and wicket-taker in the 2021 Championship season. And, judging by his innings against Glamorgan, he's still enjoying playing. Why wouldn't he carry on?
Ross Whiteley (Worcestershire) An explosive batter and bowler capable of providing medium-pace or spin, Whiteley was on the fringes of the England T20 team a couple of years ago. Although he hasn't played first-class cricket for almost two years, his middle-order hitting may render him an attractive T20 signing. Riki Wessels, now aged 35, is also out of contract.
Sam Wisniewski (Yorkshire) A left-arm wristspinner, Wisniewski is only on an academy contract at Yorkshire, but impressed sufficiently in a couple of T20s last summer that Jonty Rhodes signed him to represent Pune Devils in the T10 league. He's previously been a semi-regular face at England net sessions where he has been used to familiarise batters with the challenges presented by fellow left-arm leggies such as Kuldeep Yadav.
George Dobell is a senior correspondent at ESPNcricinfo