Liverpool manager Jurgen Klopp admitted he had "no other option" but to allow midfielder Philippe Coutinho to join Barcelona for £142m earlier this week.
The 25-year-old Brazilian joined the La Liga leaders on Monday after spending five years with the Reds.
Coutinho was linked with Barcelona in the summer, but stayed at Liverpool and scored 12 times in 20 appearances this season before his move to Spain.
Klopp also refused to rule out striker Daniel Sturridge, 28, leaving the club.
The England international has only started five Premier League games this season and has been linked with Southampton and West Ham.
"That is part of the transfer window so I have nothing to say about it," said Klopp. "We will see. Until 31 January there are a lot of things that can happen in the transfer window, not only with Daniel."
Coutinho scored 54 goals in 201 league and cup appearances for Liverpool after joining for £8.5m from Inter Milan in January 2013.