The Teessiders spent over £50million following their relegation from the Premier League when Garry Monk was appointed at the Riverside.
Boro brought in 11 players during that transfer window in their attempt to return to the top flight, and it’s fair to say the signings have been mixed.
The exits of Assombalonga and Fletcher, who both signed four-year deals when they arrived at Boro, means that Jonny Howson and Marvin Johnson are the only players left at the club who signed when Monk was in charge.
We take a closer look at the other players who joined Boro during that period, including loan deals, and what has happened to them since.
There are 11 players on the list.
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1. Jonny Howson
The standout signing on this list. After a challenging start at the Riverside, Howson, 32, has become a key player for Boro and was made club captain earlier this season.
Photo: Stu Forster
2. Cyrus Christie
Since leaving Boro for Fulham, the right-back made 67 appearances for the Cottagers. Christie has spent this season on loan at Nottingham Forest, where he has been first choice, yet he'll be out of contract this summer.
Photo: Alex Pantling
3. Martin Braithwaite
Who would have thought a player who couldn't get in Tony Pulis' side would end up playing for Barcelona. The Dane has made 26 league appearances for the Spanish giants this season.
Photo: Eric Alonso
4. Britt Assombalonga
Boro's record signing has endured a disappointing season at the Riverside, scoring just five league goals, and is now set to leave on a free. The striker will depart with 47 goals in 161 appearances for the Teessiders.
Photo: Laurence Griffiths