John Hartson has launched a blistering attack on St Johnstone defender Hayden Muller over his foul on Ryan Kent that allowed Rangers back into the match on Saturday.
The Celtic legend admits he couldn't believe what he was seeing when the 19-year-old rashly fouled Kent to let Kemar Roofe step up and equalise.
James Tavernier then went on to score a stunning winner but it was the foul by Muller that left Hartson baffled and he insists that's why the 19-year-old is at St Johnstone instead of a higher level.
The teenager is on loan at McDiarmid Park from Millwall and is getting the chance to develop at St Johnstone under Callum Davidson.
He was booked for a horror tackle on Kent in the first half that he was arguably lucky not to be sent off over, and Hartson has urged him to start using his head.
He told GoRadio: "St Johnstone go 1-0 up with a decent goal and then the boy Muller...
"You think to yourself 'this is why you're at St Johnstone, by the way, no disrespect, because you do reckless and stupid things'.
"Why go and tackle? Why go on your backside and slide tackle in the box? He brings down Ryan Kent when he's going absolutely nowhere.
"You give a penalty away and allow Rangers to come back into the game. Not using your head, not using your savvy, not using your football intelligence.
"Then, in all fairness, Tavernier scores a goal worthy of winning any game and they go on and win it."
