The Brazil international has already expressed his desire to leave Jurgen Klopp's side in the summer transfer window and has also handed in a transfer request.
However, Liverpool are adamant that the 25-year-old will not be allowed to leave the club this summer and that has seen them reject three bids from Barcelona. The La Liga giants third bid is believed to be in the region of £114m ($146.1m).
According to reports, the Catalan club are preparing a fourth bid for the former Inter Milan man, with the latest one believed to be around £136m ($174.3m).
The former Newcastle United and Blackburn Rovers manager has urged the Reds to cash in on Coutinho as he believes the South American is not a "game-changer." Souness opined that Sadio Mane is more of a key player for Klopp's side this season.
When talkSPORT asked who is Liverpool's most influential player, Souness said: "That would be Sadio Mane. Coutinho is six, seven goals a season. Does he turn up in the real big games? Mane is the man for me.
"Players normally get their way at the end of the day and, with the sort of cash that is being offered now, I'd be snapping their hand off.
"That kind of money you can't say no to. Is he that good? For that sort of money you want a player that is a game-changer, the difference in big games, and I don't see him as that.
"Yeah, he is an attractive little footballer. He is neat and tidy on the ball, he wrong-foots people, he scores some wonder goals, but at that sort of level, I would take the money. I don't see him being a Suarez or a Neymar."
Coutinho has not featured for Liverpool in a competitive fixture so far this season as he is recovering from a back injury.
Despite all the transfer speculation, Klopp has admitted that he would welcome the playmaker back with open arms into the first-team squad once he recovers from injury.