Coutinho - who has scored six times in 14 appearances this season - is expected to miss the rest of 2016 after he appeared to suffer a severe ankle injury against Sunderland on Saturday afternoon.
The Brazilian has arguably been Liverpool's best player this season, and Carragher is unsure whether Jurgen Klopp will be able to fill the void left by the playmaker.
The 38-year-old told Sky Sports News: "It could be huge. He's Liverpool's best player.
"I think Liverpool's XI, playing week in week out, can match up to almost any team in the league [but] have they got the squad the other sides have got? I don't think so, to be honest."