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.
Shakhtar Donetsk's Willian wants to continue to produce star performances to attract transfer interest from some of Europe's heavyweight clubs.
The Brazilian has enhanced his reputation with impressive displays against Chelsea in this season's UEFA Champions League.
Willian has in the past been linked with a move to Stamford Bridge and Tottenham Hotspur and he remains keen to one day make a move to a big club.
"I'm very happy with my moment at the club and I intend to keep living this moment," he told Globo Esporte.
"As for a possible transfer, there will be offers for sure and I work so that it happens.
"My club and my representatives will decide my future. I'm focused on helping Shakhtar to keep making history in the Champions League."