Benju Siegrist's challenge on Fashion Sakala should have resulted in the keeper seeing red, according to Richard Foster.
The Dundee United keeper conceded a penalty and was booked after bringing down the Rangers forward.
The foul led to skipper Jamies Tavernier putting the Light Blues in front from the spot.
But the challenge was more severe than the referee admitted, Foster thinks.
The incident provided a big talking point on BBC Sportscene as the pundits discussed the clash that saw Rangers defeat Tam Courts' Dundee United side 2-0 at Ibrox.
The Partick Thistle star reckons the challenge would have sent the guilty party packing anywhere else on the pitch.
"That's a shocking challenge," he said. "If that's an outfield player it's a red card all day long.
"I don't even know what Siegrist is thinking about there because at no point does it look like he's even trying to get the ball.
"He just absolutely cleans Sakala out. And Sakala's lucky that leading foot doesn't catch him because it's knee height, quite a dangerous tackle."
Foster went on to praise Rangers' Aaron Ramsey who played his part in winning the penalty.
The Welsh international latched onto a long pass forward to start off some good link up play by the Ibrox side.
"It's good play from Ramsey," the ex-Gers defender added. "He starts the move with the run, he keeps it going and he's just always on the move.
It was a pretty comfortable afternoon for Gio van Bronckhorst's men who doubled their lead through Manchester United loanee Amad Diallo.
The victory saw Celtic's title celebrations delayed at least until Wednesday night's full fixture card.
