Barcelona veteran Luis Suarez is reportedly poised to move to Atletico Madrid.
Manchester City are still reportedly attempting to prise Kalidou Koulibaly from Napoli.
Celtic had no qualms about Boli Bolingoli leaving the country this time, as the player who embarrassed the club joined Istanbul Basaksehir.
Celtic have bolstered their defence with the signing of Brighton and Hove Albion defender Shane Duffy.
One year after seeing Liam Morrison leave for Bayern Munich, Celtic have lost Barry Hepburn to the Bundesliga champions.
Celtic will not be in the 2020-21 Champions League after falling in the second round of qualifying to Ferencvaros.
Mohamed Elyounoussi scored twice in a strong showing from Celtic as they eased to victory in their first Champions League preliminary game.
After four years with the club, Claudio Bravo has left Manchester City and becomes a free agent. A return to LaLiga is expected.
Scottish champions Celtic have signed Albian Ajeti from West Ham for an undisclosed fee, with the striker joining on a four-year deal.
Celtic's scheduled games against St Mirren and Aberdeen have been postponed, the SPFL confirmed on Tuesday.