We take a look at some of the memorable 'panic buys' the Teessiders have made over the last 20 years – from deadline day deals to hyped-up arrivals. Scroll down and flick through our picture gallery to see the full list of players who have since left the club:
1. Adlene Guedioura
It was clear the Algerian midfielder wasn't Boro's first-choice target during the 2017 January window. After signing on deadline day, Guedioura made just five Premier League appearances for the Teessiders for the remainder of the season which ended in relegation. Photo: Alex Morton
2. Carlos De Pena
Little was known about the Uruguayan winger who signed for Boro from native side Nacional in 2015. De Pena struggled to make an impact as the Teessiders reached the play-off final that campaign and made just 10 appearances in all competitions. Photo: Martin Willetts
3. Kei Kamara
Boro needed a striker in the final hours of the 2013 summer transfer window and found the funds to buy Sierra Leone international Kamara from MLS side Sporting Kansas. The striker scored four goals in 25 appearances for the Teessiders and was quickly moved on following the arrival of Aitor Karanka at the Riverside. Photo: Tom Dulat
4. Lee Miller
Miller was part of the influx of SPL players who were signed by Gordon Strachan. After joining Boro from Aberdeen, the striker made just 13 appearances for the Teessiders and failed to score. Photo: Getty Images