John, who can operate as a left-back or as a left wing-back, played with Marshall at Cardiff City in England.
The 22-year-old Wales international, who joined Rangers on a season-long loan deal from Cardiff in the summer transfer window, has praised the current Hull City goalkeeper.
“We did have a good few goalkeepers there during his time, including David Marshall,” John told Herald Scotland. “It’s always the problem with goalkeepers, if one is doing well then that’s you out the team.
“David Marshall had his amazing league performances in the Premier League when we were up there so it’s hard for players to get into the team when someone like that is doing so well.”
Craig Gordon is the first-choice goalkeeper at Celtic at the moment, but the Scotland international is prone to making mistakes.
Dorus de Vries has failed to provide the former Sunderland custodian with any competition, and it would be a wise idea of manager Brendan Rodgers to make a move for Marshall and solve the problem between the posts.
Marshall is also a Scotland international, but the 32-year-old is struggling for playing time at Hull in the Championship in England at the moment.
Having gained extensive experience playing for Norwich City and Cardiff, the Scotsman would be a smart signing for the Bhoys, especially as he is a former Celtic player and knows what the club is all about.