Atletico Madrid have completed the signing of midfielder Augusto Fernandez from La Liga counterparts Celta Vigo.
The 29-year-old, who has won nine caps for Argentina, joins up with Diego Simeone's squad on a three-and-a-half-year contract.
Fernandez's impressive form for Celta, who he joined in 2012, has helped the club to lie fifth in the Liga standings this season and persuaded his former River Plate boss Simeone and Atleti to make their move.
Atletico Madrid sporting director Jose Luis Perez Caminero told the club's official website: "He's a player of proven experience in La Liga, who will bring quality and competition to a great midfield such as ours. His signing will help us to face the demands of having to play three competitions.
"At the club we are delighted with his arrival and during his stay in La Liga we have been able to confirm that he has great technical qualities."
Fernandez played 78 minutes of Celta's 1-0 loss at home to Athletic Bilbao on Wednesday, but has not been named in Atletico's squad to face Levante on Saturday.