Rangers manager Mark Warburton has stated his frustration at Niko Kranjcar’s knee injury, saying he is devastated for his player after working so hard to get into peak condition since his arrival at the club.

While the length of Kranjcar’s layoff has yet to be determined, Warburton couldn’t hide his disappointment in being denied the talents of his midfielder for what is likely to be a considerable period of time.

“Niko had the scan but, with those type of injuries, you get inflammation – and that hides the true picture,” Warburton said.

Read more: Graeme Souness - Financial restraints mean Mark Warburton is operating with one hand tied behind his back

“So we have to wait maybe another seven days to get a specialist opinion on where we are. We need the knee to settle down and the inflammation to reduce to get a better picture of it. We will hopefully know in a week’s time.

“It wasn’t a challenge. He was just doing what Niko does, a turn where the ground, players, posts and trees all moved to the side because of the way he moves his body – but unfortunately his knee gave way in that movement.

“Either way, it’s going to be a matter of weeks, not days. We don’t know how many weeks it will be. Hopefully, touch wood, it won’t be the worst case scenario.

Read more: Graeme Souness - Financial restraints mean Mark Warburton is operating with one hand tied behind his back

“Niko is obviously frustrated, as much as I am, as much as everyone here is. Because we know how hard he’s worked.

“He’s been the ultimate professional and was reaping the rewards. So there is obvious frustration for everyone concerned.”

One positive for Rangers from Sunday’s clash with Celtic was the outstanding performance of goalkeeper Matt Gilks, but Warburton revealed it will be regular number one Wes Foderingham who is in goal when St Johnstone travel to Ibrox tomorrow night.

“At the moment I don’t think Wes has done anything to justify being dropped or rested,” he said. “Matt know he has to be patient and work hard every day – which he is doing.

Read more: Graeme Souness - Financial restraints mean Mark Warburton is operating with one hand tied behind his back

“I played Matt in the qualifying rounds and then the knockout rounds and because we are playing in the semi-final I say ‘Sorry Matt we’re playing Celtic I’m going to play Wes’? What does that say to him about my opinion of him?”