The current Derby County head coach has been heavily linked with the post at St, James' Park, which will be vacant in the summer when John Carver's deal expires.
Murphy, who worked with McClaren during his England career, believes that there are problems at Newcastle which would make his job difficult.
"He's one of the best managers I've worked with in terms of his coaching and his tactics, but the problem I think is the players," Murphy told talkSPORT.
"If they don't change then he'd struggle."