Murphy, who represented Liverpool in midfield himself from 1997-2004, recognises the faith that manager Jurgen Klopp has in his big-money signing and does not rule out the possibility of Keita being offered a new contract.
Speaking to BeMyBet, Murphy said: "It's a bit of a conundrum that one. I think he's (Keita) probably the signing that hasn't exceeded expectations. He's been a little bit underwhelming. He's had some terrific games and he's shown some good quality. He understands the role, or he's understanding the role more and more, in Klopp's side and he's played him in some big games.
"There is definitely some trust there and I think Klopp believes there's more to come from him. I don't think he'll be leaving. I know there are some supporters that would be happy to move him on and bring somebody else in. But I think that the problem they would have at the moment, is that they wouldn't recoup the money that they spent on him.
"This is a big season for him (2022-23). I think this has to be his most productive and most consistent season as a Liverpool player. I think if we are talking this time next year and he's still been a little bit in and out, not really produced the form that he's capable of, then I think he probably will move on. But I think Klopp believes in him. He wants him to do well. As long as he stays fit, we'll see him play more and more this season."