Raging Tony Docherty accused St Johnstone skipper Liam Gordon of being guilty of an “almost life-endangering” challenge on Dundee substitute Michael Mellon.
The incident happened at the end of the cinch Premiership match that the Dark Blues won 2-1, with the Saints defender involved in a clash of heads with the on-loan Burnley striker.
After a lengthy stoppage, Mellon was stretchered off and taken to hospital in an ambulance.
Dundee boss Docherty said: “He’s not great. I’d like the referee to comment on that.
“For me, that was almost life-endangering that challenge.
“And to not even get a booking for it…
“Michael is a top boy in our team and I’m concerned for him because he took a really bad blow to the back of the head.
“Luckily we have a brilliant doctor here, Dr McCormack, who didn’t pay any attention to the referee and ran onto the pitch.
“It was a sour note at the end of the game and the player’s welfare is the most important thing.”
Dundee had gone behind to an early Matt Smith goal but stormed back after the break with a controversial penalty from Luke McCowan and a late header from Jordan McGhee.
Docherty added: “My team were absolutely outstanding. Their level of performance for the majority of the season has been high but here they showed a real bravery.
“Every player deserves huge credit.”
Saints boss Craig Levein slammed the decision to award a penalty for the incident involving Gordon and Amadou Bakayoko, with referee David Munro’s attention drawn to what happened by VAR Don Robertson.
The manager said: “It’s not VAR, it’s people making the decisions.
“The decision-making for me was ridiculous.
“Look at every set-piece in a game and you could find something that could be called a foul.
“Firstly, Gordy’s arm is raised by David Keltjens. It’s raised Gordy’s arm and it’s on the shoulder.
“The referee is none the wiser but somebody decides it’s a good idea to intervene.
“That’s not a clear and obvious error.
“It’s very simple. It’s not VAR, it’s somebody sitting in a wee booth somewhere thinking ‘you know if I’m pretty bored I’ll maybe call the referee over for this one’.
“Nobody knows what’s going on.
“That’s the third one of those that has gone against us.
“Maybe Dundee haven’t had much luck recently but we certainly haven’t, that’s for sure.
“What really, really annoyed me was our response to it was abysmal.
“I apologise to our supporters for our second-half performance because it wasn’t good enough.”