Atletico Madrid confirmed the signing of Brazilian defender Gabriel Paulista from Valencia on Wednesday until the end of the season.
Valencia said the 33-year-old centre-back had "reached a deal to end his contract" with the club.
Paulista joined Valencia in 2017 from Premier League side Arsenal, playing 213 times for Los Che.
Atletico centre-back Jose Gimenez was injured against Valencia in the capital club's 2-0 win on Sunday, and is expected to miss three weeks.
With key games against Real Madrid in LaLiga and Athletic Bilbao in the Copa del Rey approaching, as well as the return of the Champions League, Atletico moved quickly to find a replacement.
Diego Simeone's side have also signed midfielder Arthur Vermeeren from Royal Antwerp and goalkeeper Horatiu Moldovan from Rapid Bucharest in the winter window.
Valencia also loaned 21-year-old winger Peter Federico from Real Madrid on Wednesday.