Jamie Dalrymple has left Middlesex, who have completed the signing of Ollie Rayner on a three-year contract.
Dalrymple made two championship hundreds after returning to the club in May, the first being an innings that helped guide Middlesex to a crucial victory over Surrey at Guildford.
He also claimed vital wickets in the same match and the game that followed against Derbyshire at Lord’s.
“His contribution on and off the field was invaluable. With the bat he scored vital runs at crucial times and he also claimed important wickets,” said Middlesex managing director of cricket Angus Fraser.
“I have seen very few cricketers more committed or harder working than Jamie and during his time with Middlesex he set the right example to the rest of the squad.
“His leadership experience was valuable too, helping to get a young side over the line when things got a little tight at the end of the season.
“However, his passion lies in leadership and man-management roles and these are not positions that are currently available at Middlesex.”
Dalrymple said: “I’d like to thank Middlesex and Angus Fraser for the opportunity to return to play this season after the difficulties I had last winter.
“Cricket has been my passion for many years now and my experiences so far have shown me how much I relish the challenges of leadership and management. Unfortunately that opportunity is unavailable at this time.
“I now have a chance to consider whether I want to keep playing, to look for a leadership role within the game or to move on to something completely different.”
Rayner had two spells on loan from Sussex last season and was an important player for Middlesex as they won promotion.
His return comes the day after the club handed Adam London a contract until the end of next season and signed bowler Gurjit Sandhu on a two-year professional deal.
Fraser said: “Ollie is an exciting and talented young cricketer who contributes with bat, ball and in the field. He made an extremely positive impression during the loan periods he spent with us and we are delighted to have him on board.
“Ollie has presence on a cricket field and works extremely hard at his game. As with all young cricketers there is work to be done but he has the potential to be an extremely fine all-round cricketer. We are all looking forward to working with him on a full-time basis.”