Boro boss Neil Warnock will no doubt be assessing the free agent market, with 168 players nearing the end of their current deals in the Championship.
The Teessiders are also facing contract decisions of their own, with Marvin Johnson, Nathaniel Mendez-Laing and goalkeeper Jordan Archer assessing their futures.
There are plenty of others in the same boat, including players who have previously played for Boro.
Some may even interest Warnock as he looks to strengthen his squad in several positions and challenge for promotion during the 2020/21 campaign.
We’ve taken a look at a number of the former Boro players who are set to become free agents in the coming months, as well as their situations heading into an uncertain summer.
1. Stuart Downing (Blackburn)
The Boro-born winger, now 36, signed a one-year extension at Ewood Park last summer but hasn't made many starts this campaign. Photo: Alex Pantling
2. Mo Besic (Everton)
Following loan spells at Boro and Sheffield United, the Bosnian hasn't played for Everton since 2017. Besic hasn't made a competitive appearance since January 2020. Photo: Getty Images
3. Joe Bennett (Cardiff)
Bennett has been at Cardiff since 2016 but is set for an extended spell on the sidelines after suffering an anterior cruciate ligament injury. His contract is also set to expire. Photo: George Wood
4. Jamal Blackman (Chelsea)
After several loan spells, the 27-year-old goalkeeper is still contracted to Chelsea. Blackman has made 22 Championship appearances while on loan at Rotherham this season. Photo: Jan Kruger