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:
9. Dillon Phillips (Charlton)
Boro are said to be looking at other goalkeeping options after Aynsley Pears and Dejan Stojanovic were rotated at the end of last season. Sky Sports reported last month that a couple of Championship clubs, including Boro, were intereted in Phillips, 25, following Charlton's relegation from the Championship. Photo: Alex Pantling
10. Jordan Jones (Rangers)
The 25-year-old has been linked with a return to the Riverside for the last few months and hasn't featured in Rangers' first five league games this season. It's believed Boro are interested in a loan move but are prioritising other positions first. Photo: Ian MacNicol
11. Morgan Fox (Signed for Stoke)
The left-back was linked with several Championship clubs, including Boro, after turning down a new deal at Sheffield Wednesday but ended up at Stoke. Photo: Clive Brunskill
12. Loic Mbe Soh (PSG)
A report in French newspaper L'Équipe claimed Boro and Norwich had made approaches for the 19-year-old centre-back but we haven't heard anything since. Photo: Lewis Storey