Changes in the law in 2016 meant players who’re left requiring treatment after being fouled don’t have to leave the field if the opponent is booked for the challenge.
However, referees are allowed to ask players to leave if the recovery is taking longer than expected.
Such an instance occurred during Saturday’s 1-1 draw between Dundee and Kilmarnock where away defender Jack Hendry was taken out by a strong challenge from Calum Waters.
Hendry needed lengthy treatment and was instructed to leave the play by the match official, something which angered McCann.
He told the Dundee Telegraph: “The fourth official is saying Waters mistimed it but for me it was like a car crash.
“He goes in at such a speed, and I know you can say he mistimed it, but I thought there was a clear split second where he [Hendry] knocks it past him and the impact means it could have been a real serious one.
“It wasn’t given but what I’m more upset about is this stupid rule.
“I was under the impression if your opponent gets booked, you didn’t need to leave the pitch.
“I asked the fourth official why Jack had to leave the pitch and he said if the treatment takes too long he has to go off.
“The guy’s just been smashed in the middle of the pitch and we’re getting punished because it takes him a wee bit longer to recover — it’s ridiculous.
“He’s our biggest player, he’s our biggest threat and we’re in a good position with the free-kick.”