The sports media outlet claim that Boro boss Aitor Karanka is looking to bolster his defensive options, and sees the 26-year-old Brazilian as an ideal acquisition.
Middlesbrough manager Aitor Karanka
The former Manchester United defender has true pedigree within the game and has a Premier League winners medal to his name from his time at Old Trafford.
He moved to the Welsh outfit in January 2014 after then United manager David Moyes deemed him to be surplus to requirements and he has gone on to make 69 appearances for the Bluebirds.
ESPN go on to report that Cardiff are prepared to cash in on the Brazilian as he enters the final year of his contract with the club.
Fabio celebrates scoring for Cardiff
The Teesside outfit achieved promotion to the Premier League last season after an impressive campaign that was underlined by their defensive solidarity.
The report claims that Fabio originally came to the Boro boss' attention when he scored a superb goal against his side last season, and he has been keeping tabs on him ever since.