Barcelona have had two bids of £72million and £90m for Coutinho swiftly rejected by Liverpool but the Brazilian responded to the club's stand by submitting a transfer request.
That was also rejected by Liverpool, who's owners Fenway Sports Group have insisted the player will not leave before the end of the transfer window.
Express Sport understands Barcelona are ready to break the £100m barrier for the Liverpool star and Antonio reckons the Reds have to consider letting Coutinho go before the end of the window.
He told BBC Sport's MOTD2 Extra: "As a player, Barcelona come knocking you go.
Liverpool fans claim they don't need Coutinho after Mane, Firmino and Salah goals
Sat, August 12, 2017
Liverpool fans claim they don't need Philippe Coutinho after Sadio Mane, Roberto Firmino and Mohamed Salah all score against Watford
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I believe as a player, the club should let him go because his head has been turned
"But I feel Liverpool is doing the right thing for the club because he is their best player, he makes things happen from nothing and standing their ground is decent.
"But then again would you want a player that doesn't want to be at your club?
"I believe as a player, the club should let him go because his head has been turned.
Philippe Coutinho's future is uncertain
"The effect it has on the group, the effect it has on the player himself.
"He's never going to be the exact same player because his mind and body is no longer with Liverpool.
"You've got to let him go because he's not going to be the same player that he was last year."