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.
Shinji Kagawa has confirmed he has held talks with Manchester United manager Sir Alex Ferguson fuelling rumours of a switch to England.
The Japan international rejected the offer of a new contract with Borussia Dortmund as he sets his sights on a move to the Premier League.
And the Red Devils appear to the head the queue for the midfielder's signature after he exchanged "good words" with Ferguson during a two-hour meeting.
"It was good that I was able to meet him in person and talk," Kagawa told reporters on his return to Japan to prepare for the international friendly against Azerbaijan.
"I want to think hard before making my decision. I want a team where I can take on challenges."
The 23-year-old, who is expected to command a fee in the region of £10m, has also been linked with Chelsea, Arsenal and AC Milan.