Sky Sports reported on Saturday that Rangers boss Graeme Murty is close to signing the Brighton & Hove Albion winger, who will join for around £1 million.
The 28-year-old grew up as a Rangers fan and faced his boyhood club on plenty of occasions during a seven-year stint in Motherwell's senior setup until 2013.
Gers boss Murty could do with a wide option like Murphy and former Rangers man Johnstone is certain that he will prove value for money in Glasgow.
"I must admit that I was surprised when I learned that Rangers were prepared to pay a ransfer fee of around £1 million to get Jamie Murphy. But if Murphy puts pen to paper then it will be money well spent. It will be a great bit of business," he told The Glasgow Evening Times.
"He is a smashing footballer. He has played at a good level down south with both Sheffield United and Brighton. Plus, he knows the Scottish game.
"In fact, I think he will be nothing short of a revelation at Ibrox.
"He is the sort of player who gets bums on seats and then gets fans on their feet. He is the kind of player who supporters love to watch."
One big positive of signing a left-sided attacker like Murphy is that it'll allow Josh Windass to operate in his preferred number 10 role.
With Carlos Pena seemingly on the move, Windass is far more important now and he is simply much more effective in a position behind the striker(s), as opposed to the left or right of them.