Kileeen was offered a contract to stay at Durham but turned it down and wishes to explore his options elsewhere.
An academy and pathway graduate, Killeen represented the club throughout the age groups from Under 11s right through to the first team, signing his maiden rookie contract in 2022.
His first-class debut came earlier this season against Zimbabwe A in Harare, while his maiden County Championship appearance was against Somerset in May.
The 20-year-old claimed his maiden first-class five wicket haul against Somerset with 5-36, while he has nine List A wickets to his name from nine matches.
North said: “We’re obviously disappointed to lose a young player in Mitch who has progressed through our pathway, but we fully understand his reasons for wanting to explore a new challenge at Essex.
“Mitch was in our plans as a club moving forward and that was evident with the offer of a new contract, however we are grateful for his efforts in a Durham shirt, and we wish him the best of luck for the future.”
Killeen said: “I would like to take this opportunity to thank everyone at Durham who has
helped me from pathway to becoming a professional cricketer.
“I have loved my time at the club but feel now is the right time to move on and seek out new opportunity. I would like to wish Marcus, Cambo and all the players continued success for the future.
“Durham will always be my home and look forward to returning in the near future.”
McAlindon will also leave Durham following the completion of his rookie contract.
The 21-year-old made his Durham debut in 2022 and went onto take 15 wickets in 13 senior appearances, claiming 2/63 on his Durham first-class debut came against Derbyshire.
The Carlisle-born cricketer progressed through the Cumbria pathway before joining the Durham Academy in 2020 and then signing his first rookie deal two years later.
North, director of cricket, said: “Stan will leave us at the end of the season, having been a
member of our squad for the last five years. We wish him all the success in his future endeavours.”
