Keith Curle believes referee Tony Harrington should have reduced Leyton Orient to 10 men just 20 minutes into Saturday's Sky Bet League Two clash at the PTS Academy Stadium.
With the score at 0-0, Orient midfielder Dale Gorman launched himself into a over-the-ball, strong and late challenge on Nicky Adams as the Cobblers attempted to set off on a counter-attack.
It looked from the stands to be a clear red card offence, but the official deemed the incident only worthy of a yellow card, much to Gorman and Orient's relief, with the 11-man visitors going on to win the game 1-0.
Harrington, who has been a regular whistler at Championship level for the past four seasons, took his time over his decision, before allowing Gorman to stay on the field of play, and Curle believes he made the wrong call.
"I think a lot of referees would have sent the lad off for that tackle," said the Town boss.
"I have seen it back, and you have to respect the referee's decision to step away from the incident and take his time to make his decision.
"But my initial reaction was 'that is a bad tackle', and in hindsight and having watched it back, my thinking is 'that is a bad tackle'.
"He is a Championship referee, so what you would like to say is as a Championship referee they get more decisions right than not, but a bad tackle is a bad tackle."
And Curle continued: "It would be interesting to get the opinion of a lot of referees.
"I think a large majority would say 'that is a reckless, out-of-control tackle, above the ball, that is endangering an opponent'. It would be violent conduct, however you want to categorise it.
"The fourth official deemed it reckless enough for a caution, but not reckless enough for a red card.
"Then there was another incident when we put the ball into the box and the lad pushed Harry Smith. The fourth official said 'it was a push, but not enough of a push for a penalty'."
The Cobblers are back in action on Tuesday night when they travel to Cambridge United in the Leasing.com Trophy.