Forest are currently in mid-table, hoping to regroup and make a late push for the play-offs, but they need to add to their squad to do so. Here are three former players Karanka could look to bring to the City Ground:
Nottingham Forest could do with a couple of extra bodies in the central midfield area. Chris Cohen has had his injury problems this season, which leaves David Vaughan, Ben Osborn and Liam Bridcutt as their only other options in that position.
Adam Forshaw played a key role for Middlesbrough in helping them win promotion to the Premier League under Karanka in 2016. He has been in and out the team at the Riverside, so a move for the former Brentford man would be an astute bit of business as he is accomplished at this level.
Karanka may want to bring a striker to the City Ground in the January window. Daryl Murphy is out injured while youngster Ben Brereton has been leading the line in his absence. Tyler Walker and Jason Cummings are Forest's other forward options but again they are young and inconsistent.
Patrick Bamford served Karanka well at Boro. He scored 19 goals in 2014-15 season as the Teesiders reached the play-off final. The former Real Madrid assistant manager re-signed him last January for Middlesbrough, but it has not worked out for the former Chelsea man so a reunion with Karanka could revitalise his career.
Daniel Ayala has played over 120 times for Middlesbrough and was most influential during Karanka's spell at the club. The 27-year-old is a commanding defender who has excelled at Championship level in the past.
He had a spell on loan at Forest during the 2012-13 season so is familiar with the club. He would add much needed competition and promotion-winning experience to the back line at the City ground.