Glasgow Rangers boss Mark Warburton has parted company with the coach following a decision to reshuffle his backroom team at Ibrox.
The 49-year-old has been associated with the Light Blues for a total of 25 years, having spent the majority of his playing career with the club before returning after retiring to be a part of the coaching team, most recently taking on the role as the club's under-20 manager.
However, the Evening Times reports that he is now set to leave following Mark Warburton's decision to reshuffle his backroom team.
And Johnstone conceded that it was a shock to hear that he will leave the Gers given his knowledge of the club, and the impact that his work has had on the first-team this past term.
"He's given his all. Apart from the short spell at Kilmarnock he's been there for his whole career. I'm very surprised. With his experience he knows what Rangers Football Club needs as he's been there seen it and done it," he told the Evening Times.
"In terms of Mark Warburton, for the first team he's not done much wrong. He's got them where they belong and playing some good stuff.
"He's taken two or three players Ian coached at under-20s into the squad so he has made a difference."
With Warburton turning to several younger players since he arrived in Glasgow last summer, it is perhaps surprising that Durrant has been released.
However, with Rangers now preparing for a season in the Scottish Premiership, Warburton may feel that the step-up in class means that fewer youngsters will be given a chance next term, and thus, it may make more sense for those knocking on the door to actually go out on loan rather than stick around for the occasional opportunity at Ibrox, which perhaps made Durrant's current role less important.