Boro made four new signings during the window, as goalkeeper Tomas Mejias, Marcus Browne, Marc Bola and Anfernee Dijksteel all signed for the club. We take a closer look at some of the players who got away and how they’ve fared since. Scroll down and flick through our gallery to find out:
13. Cameron Carter-Vickers (Stoke)
After he was linked with nearly half the clubs in the Championship, the USA centre-back completed a season-long loan deal from Tottenham to Stoke. He has been a regular for the Potters who have recorded just one league win this season. Photo: Stu Forster
14. Ivan Toney (Peterborough)
Subsequent reports have suggested Boro weren't interested in the Posh forward despite interest from elsewhere. It's easy to see why Toney was a man in demand, though, as the 23-year-old has already scored nine goals in 11 League One games this season. Photo: Jordan Mansfield
15. Mohamed Elyounoussi (Celtic)
The winger has said he had other offers in the summer before joining Celtic on loan from Southampton in the summer. Whether Boro were interested remains unclear. Elyounoussi's best performances this season have come in the Europa League after his only Celtic goal to date came against CFR Cluj. Photo: Trond Tandberg