Centre-back Grant Hall is the only player who has joined the Teessiders ahead of the 2020/21 campaign, while other transfer targets have moved elsewhere.
Scroll down and flick through the pages of our picture gallery to see every player who has been linked with Boro this summer and what has happened to them since:
5. Josh Windass (Wigan)
Boro were credited with interest in the attacking midfielder in June yet reports have quietened since then. It's been claimed three clubs have met Wigan's valuation for Windass, 26, including Sheffield Wednesday and Preston. Photo: Charlotte Tattersall
6. Ben Gibson (Burnley)
Boro's former captain wants to leave Burnley but still has two years left on his contract. A loan move back to the Riverside would require the Clarets to pay a large part of the defenders wages, while Norwich and Nottingham Forest have also been linked with the centre-back. Photo: Alex Livesey
7. Kieffer Moore (Signed for Cardiff)
Boro were heavily linked with the towering frontman who instead signed for Championship rivals Cardiff for around £2million. Photo: Nathan Stirk
8. Lyndon Dykes (Signed for QPR)
A player who has reportedly been on Boro's radar for some time, yet the 24-year-old ended any sort of speculation by signing for QPR earlier this month. Photo: Getty Images