CHRISTCHURCH, NEW ZEALAND - FEBRUARY 27: The injured Reed Prinsep of the Crusaders is brought off the pitch by a St. John Ambulance vehicle during the round one Super Rugby match between the Crusaders and the Chiefs at AMI Stadium on February 27, 2016 in Christchurch, New Zealand. (Photo by Kai Schwoerer/Getty Images)

Crusader coach Todd Blackadder has called for changes to the rules around substitutions after he says his team was disadvantaged on the weekend against the Chiefs.

Crusader Reed Prinsep was knocked unconscious almost immediately after coming on to the field for flanker Tim Boys in the 67th minute.

The Crusaders wanted to replace Prisnep with Boys, but were not permitted to do so, forcing them to bring on halfback Leon Fukofuka to play in an unfamiliar position.

Current Super Rugby rules state that a player who is forced off the ground due to a blood or concussion can only be replaced by a player who was in the starting XV.

The Crusaders went on to lose the match 27-21, with the Chiefs scoring a late try to win the match.

“I think common sense needs to prevail here,” Blackadder told the NZHerald.

“If Reed (Prisnep) had been able to say ‘I’ve had a head knock, I need to come off for a concussion test’, we would have been able to replace him with Tim. ”

“But the fact that he was knocked unconscious meant we weren’t able to do that.

“The law needs to be amended straight away because player welfare has to come first and teams shouldn’t be penalized for players being knocked unconscious.”

The Crusaders host the Blues in Christchurch this Friday night.