Coutinho started the season in fine form for Liverpool, scoring nine goals by the end of November.
However, his form has waned since sustaining an ankle injury at home to Sunderland.
He returned to action against Southampton on January 11 but has struggled to have the same impact as before.
And Merson believes Coutinho is overrated – and reckons Chelsea star Eden Hazard puts him to shame.
Philippe Coutinho isn't world class, according to Paul Merson
Philippe Coutinho and Co. in Liverpool training ahead of FA Cup clash with Wolves
Fri, January 27, 2017
Express Sport brings you the best pictures from Liverpool's latest training session ahead of their FA Cup Fourth Round clash with Wolverhampton Wanderers at Anfield on Saturday (3pm)
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Liverpool were hard at work on Friday night ahead of their clash with Wolves
“Jurgen Klopp says Coutinho is world class. But he’s not. He’s not a Cristiano Ronaldo. He’s not even an Eden Hazard in my opinion,” he told the Daily Star.
“If he’s on top of his game, and Hazard is too, I know who I’d rather have in my team.
“Coutinho is not going to rip it up on his own. How many games has he won for Liverpool this season?
“Jamie Carragher has criticised him before for not having enough end product, and he’s right.
Philippe Coutinho recently signed a new deal at Liverpool
“Coutinho’s scored five goals in the league. Joe Allen at Stoke has scored as many as that. Leroy Fer at Swansea has scored more.
“A lot of his goals are worldies as well. They dry up sooner or later. He needs to find other ways to score.
“He also has five assists but that doesn’t even put him in the top ten this season. So £150,000-a-week is a lot to be paying him.
“I don’t even think he’s Liverpool’s best player. Sadio Mane is probably more important to them and they’ve really missed him.”
Paul Merson would rather have Chelsea star Eden Hazard in his team
Merson also slammed the Brazil international for his failure to fire them through to the EFl Cup final at Southampton’s expense.
“Coutinho played in both legs of the EFL Cup semi final against Southampton and Liverpool didn’t score,” he added.
“Now they’re in all sorts of trouble. It’s one win in seven and if they lose to Chelsea on Tuesday you wonder if they’ll even finish in the top four.
“Those are the games you expect your big players to show up in. Those are the games you pay them the big money for.
“So it’s time for Coutinho to show up. His team needs him. He hasn’t scored since November. Yes, he’s been injured but he’s played seven times since then.”