Barry Ferguson suspects Gio van Bronckhorst has been pivotal in Alfredo Morelos ' return to form.
The Rangers striker has sparkled in front of goal under the new manager - scoring four times in his last five appearances, including the second in Sunday's 2-0 victory over St Mirren.
Morelos' indifferent early season form attracted criticism but Ferguson has been impressed by the recent uptick.
And the former Rangers captain believes Van Bronckhorst may have given the Colombian "a kick up the backside" to get him going again.
"His goal sums his up just now," Ferguson told Go Radio. "It's a good header - but he's first to react, that's sharpness, that's fitness.
"When you're fit, you're fit upstairs and that's what happened with his goal against St Mirren.
"He was first to react before any St Mirren defenders.
"No doubt about it, I've seen a major difference in him since Gio's come in, and that's maybe what he needed.
"Maybe he needed a kick up the backside because there's no doubt he's got so much quality.
"(Steven Gerrard) always supported him in public but, I'm sure, behind closed doors he wouldn't have been happy with his performances or maybe his fitness levels.
"But there's a clear change in him and maybe Gio's had that input, maybe he's sat him down and said: 'I need you to be fitter because you're a big player for us.'
"When he's on that type of form he is a big player, he's a match-winner and Rangers need players like him playing like that every single week."
