Middlesex have confirmed that Ed Joyce is leaving the county after December's Twenty20 Champions League tournament.
The Irish-born batsman is hoping a change of scenery will help him rediscover the form that earned him 17 one-day internationals for England in 2006 and 2007.
The 30-year-old is reportedly set to sign for Sussex, although they have yet to confirm the deal.
"Ed has been nothing but professional and thorough and has communicated with me through the process," Middlesex chief executive Vinny Codrington told the county's official website.
"We agreed with Ed back in September that he would be available for both Antigua and the Champions League whatever his decision as he was an integral part of our successful 2008 Twenty20 campaign.
"He leaves with our best wishes and hopefully can help bring home the Champions League title as a leaving present! We would like to wish Ed all the best in the future."
The eight-team Champions League event takes place in India from December 3-10. Middlesex qualified by winning the Twenty20 Cup and are joined by the best domestic teams from India, Australia, South Africa and Pakistan.