Celtic boss Ronny Deila says keeping his best players will take priority over acquisitions in the transfer window.
Chelsea striker Fernando Torres is understood to be set for a return to Atletico Madrid, according to Sky sources.
Ramon Nunez's Leeds contract has been terminated by mutual consent.
Nunez has not played for the club since April and was not given a squad number at the start of the season.
The Honduran midfielder's deal has been scrapped by mutual consent, and he is now free to find another club.
Nunez made 25 appearances in two-and-a-half years with Leeds following a 2010 move from Deportivo Olimpia.