Johnson, who joined Boro from Oxford United in 2017 and made 102 appearances for the club, was a regular in the first half of last season, but struggled for regular opportunities after Boro chief Neil Warnock brought in the likes of Yannick Bolaise and Neeskens Kebano during the winter transfer window.
The 30-year-old has been informed that he can move on, meaning that Jonny Howson is the last remaining signing at the club from the Garry Monk era, when the Teessiders spent millions in an infamous and failed attempt to ‘smash the division’ in the summer of 2017, a time when the club were in receipt of parachute payments.
Two expensive signings from that time in the shape of strike pairing Britt Assombalonga and Ashley Fletcher were told in April that they were free to leave the club.
Assombalonga, 28, brought in for £15m from Nottingham Forest, has been linked with a return to the City Ground with Glasgow Rangers also credited with an interest.
Former Barnsley loan forward Fletcher, 25, whose time on Teesside was afflicted by fitness and form issues following his arrival for £7m from West Ham, has reportedly agreed a deal with Premier League newcomers Watford.
Sidelined for a significant part of the campaign with a serious hamstring injury, the striker scored three times in 13 appearances for Boro in 2020-21 ahead of being released,
Former Motherwell and Millwall goalkeeper Archer, 28, who joined the club in the new year and had started in Boro’s final five matches of the campaign, has also been informed that he will not be offered a new contract.
Mendez-Laing, who successfully worked with Warnock at Cardiff, featured nine times for the club after also signing on a short-term deal in late winter, making just two starts and scoring in the win over Stoke in March.
Reports suggest that Archer and Mendez-Laing could yet be invited back to train with the side for pre-season and earn a place in Boro’s squad next term.
Prior to his spell at Boro, Mendez-Laing was serving a three-month footballing ban after testing positive for cocaine.
Striker Tyrone O’Neill, who made his first-team debut at Leeds in November, 2019, has also been released, alongside fellow young players Cole Kiernan and Tyler Williams, being told that they have not been offered new deals. Scholars George Waites and Andrew Wilson have also been released.
Boro have already made a close-season capture in the shape of QPR goalkeeper Joe Lumley, who will officially sign for the club in July when his Loftus Road contract expires.
Academy products Jack Robinson, Cain Sykes and Hayden Hackney have recently signed new contracts, while Josh Wells and Jeremy Sivi have agreed terms after impressing on trial – with Isiah Cornet and Max Metcalfe penning their first professional contracts.
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