Atletico Madrid expect to confirm the return of Brazil international Filipe Luis from Chelsea on Friday.
Luis left Atletico last summer, but Chelsea boss Jose Mourinho confirmed earlier this week that the left-back was on the verge of a return to Vicente Calderon.
Atletico are reported to have agreed to pay €16 million for the 29-year-old -- €4m less than they received for him last summer -- and the deal is set to be finalised once the Spanish club receive the necessary documentation.
"We are practically in the final process and we hope all will end well and the player can join the group as soon as possible," Atletico president Enrique Cerezo told the Spanish media.
"Negotiations are long and each day it becomes more difficult to sign new players."
The defender made 127 appearances for Atletico in his four years with the team, helping Diego Simeone's side win the 2012 UEFA Cup, 2013 Copa del Rey and La Liga in 2013-14.
He made only 26 appearances for Chelsea in all competitions this past season and just nine league starts.
He is expected to sign a three-year contact with Atletico and will follow Luciano Vietto, Angel Correa, Yannick Carrasco, Jackson Martinez and Stefan Savic in joining Atletico this summer.
OFICIAL | El portero Bono jugará una temporada más en el Real Zaragoza http://t.co/ctEQdBXCDc ¡Bienvenido de nuevo! pic.twitter.com/UoZdfsARqE
- Real Zaragoza (@RealZaragoza) July 23, 2015
Meanwhile, Atletico have announced that goalkeeper Yassine "Bono" Bounou will join Segunda Division side Real Zaragoza on loan.
The 24-year-old Morocco international also spent last season on loan at Zaragoza.
An Atletico statement read: "An agreement has been reached with Real Zaragoza to loan Bounou for next season.
"The Morocco international had been training with Atletico's first team up to now and will continue to gain playing time in Zaragoza, where he played on loan last season."
Bono made 19 appearances for Zaragoza in the 2014-15 campaign, helping the Aragon club reach the Segunda Division playoff final, where they lost to Las Palmas.
The Montreal-born player, who joined Atletico's B team three years ago from WAC Casablanca, is under contract with the capital club until June 2017.