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.
Derby defenders Gareth Roberts and Jake Buxton have signed new deals.
Both players were set to be out of contract at the end of the season.
Left-back Roberts, 34, has signed a 12-month extension while fit-again centre-half Buxton, 27, has put pen to paper on a two-year deal.
Manager Nigel Clough was delighted to keep hold of the defensive duo as he begins to make plans for next season.
"It is great news that both Jake and Gareth will be with us beyond the end of this season," Clough told the club's official website.
"We've said all along we wanted to keep the pair of them and we're delighted that they see their futures with Derby County because we see theirs with us."