The Reds rebuffed several big-money offers for the Brazilian playmaker from Barcelona over the summer, but the Stoke City veteran believes that offloading him could be the best option for the club in the long run.
"This is what happens when you've got one of the best players in the world," Adam told talkSPORT.
"It's going to just see how long the Liverpool owners stay strong - can they afford to not let him go in the January window? I think if they're nowhere near winning the league, he will go."
Barca are said to have offered more than £110m for Coutinho in the summer, and Liverpool are expected to reject further bids from the Catalan club in January.
"I think if they're nowhere near winning the league, he will go," Adam added.
"The money they're talking about - £120m - that's a rebuilding job! That will buy them the four defenders and a goalkeeper they probably need."
Liverpool are back in Premier League action this weekend when they take on Manchester United at Anfield.