Aitor Karanka has bolstered his defence with the loan signing of Fulham centre-back Fernando Amorebieta, who will stay with Boro for the rest of the season.
Meanwhile, Boro full-back James Husband has switched to Craven Cottage in a similar loan deal until May.
Amorebieta, a 30-year-old Venezuelan international, is well known to Karanka, having developed his career at the Head Coach's first club, Athletic Bilbao.
He became a regular first choice for the Basque club, playing 195 games and enjoying UEFA Cup experience. Fulham signed him in summer 2013 and he played 23 Premier League games for them in their relegation season.
Amorebieta represented the Spain U-19 side that won the UEFA Championship in 2004 before switching his allegiance to Venezuela at senior level. He has 10 caps for the South American country.
He has also played for the Basque Country national team four times.
Husband, 21, joined Boro last summer from Doncaster and has made six appearances this season in all competitions.