Hearts, third in the Scottish Premiership, had the chance to move level on points with second-place Rangers, but that all came crashing down in a disastrous first half.
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A double from Croatian forward Antonio Colak saw Giovanni van Bronckhorst's side two goals to the good after half an hour, and then the game was put to bed.
Not by a Rangers player though, but by a Hearts one, who bizarrely charged over to get involved in a touchline jostle for possession.
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Former Manchester City prospect Rabbi Matondo was holding the ball off from an opponent before Devlin made a beeline to get involved.
His tackle provoked a heated reaction from the Rangers bench and referee Steven McLean took no time at all to whip out his red card.
It's rare an official is so confident in sending a player off so quickly, but replays showed just how bad the challenge was, forcing Matondo's ankle into a nasty looking position.
"Oh dear me, what is he thinking about?" asked McCoist. "It's right down on his right ankle here.
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"Oh dear, leaves the referee absolutely no option at all, nonsense.
"I did mention before he's a fiery character, when you're 2-0 down [Hearts manager] Robby Neilson must be saying what's going on here, crazy absolutely crazy."
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Thankfully, Matondo was able to play on, and had the last laugh as his side ran out 4-0 winners.