Coutinho, 25, has long been linked with a move to the Nou Camp.
And Barcelona have stepped up their interest over the past week amid uncertainty surrounding Neymar’s future in Catalonia.
Coutinho committed his long-term future to Liverpool in January, signing a new five-year contract worth around £8m a year.
And the Reds are unsurprisingly in no rush to sell their star man.
But Barnes believes they may be fighting a losing battle.
Coutinho bagged the winner as Liverpool picked up the Asia Trophy with a 2-1 win over Leicester City on Saturday.
And Barnes has suggested his meek reaction to the strike was proof he maybe wants out of Anfield.
"You could tell by the way he reacted after he scored, with no celebration or anything, that something isn't quite right with Philippe at Liverpool," said the Reds hero, speaking to ESPN FC.
"It would be great if Liverpool keep him, but if he goes, I wish him all the best.
“Jurgen Klopp still has a good squad, so he will maximise the potential of the squad without Coutinho.
“We'd like him to stay, but if he goes Klopp will still find a way of being competitive."
Coutinho played a key role for the Reds as they claimed a fourth-place finish last season.
The former Inter Milan ace made 36 appearances in all competitions, scoring 14 goals and assisting nine in the process.