Karanka, 40, is the hot favourite to be appointed as Tony Mowbray's succesor at the Riverside Stadium with the Spaniard poised to become the club's first foreign boss.
The former Real Madrid defender spent three years as Jose Mourinho's assistant at the Bernabeu and was this week heavily linked with the vacant manager's job at Crystal Palace.
Boro would not comment when contacted by Press Association Sport but reports in the north-east claim Karanka has been offered a two-and-a-half-year contract.
Mowbray's assistant Mark Venus has been in caretaker charge and this week admitted he would like the role full-time.
But it appears chairman Steve Gibson has opted for Karanka, of whom Mourinho commented: "I think whatever club gets him, will be a lucky club.''
- Sports & Recreation
- Tony Mowbray
- Jose Mourinho