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.
Liverpool rejected three Barcelona bids and a transfer request from the player during last summer’s transfer window, but Klopp conceded they could no longer keep the player against his will.
“There was no other option,” said Klopp. “I knew there was a moment when it would come up again in this transfer window and it came up massively.
“It would have been very difficult if we say, and we could have done of course with his contract, ‘you have to stay here’.
“To use him as a player in the second part of the season, did it make sense? Do I think I can use him and can he help us? It became 100% clear, no chance. He was not ready to do that any more.”
Liverpool are fourth in the Premier League and host leaders Manchester City at 16:00 GMT on Sunday.
Their leading scorer Mohamed Salah, who has hit 23 goals in 29 appearances this season, is in contention after missing two matches because of a groin problem.