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.
Lyon have signed Portugal international defender Miguel Lopes on loan from Sporting Lisbon.
The 26-year-old right-sided defender, whose rights are still partly owned by his former club Porto, has initially joined Lyon on a one-year loan deal with the option for the Ligue 1 outfit to make the move permanent at the end of the season.
According to a statement published on Lyon's official website, Lopes underwent a medical in France on Sunday and will return to Lisbon on Monday to finalise some personal matters before linking up with his new team-mates in midweek ahead of the squad's pre-season trip to New York.
Lopes becomes Lyon's second signing of the summer after midfielder Gael Danic.