The NRL have fined Canterbury $20,000 for breaching the league’s new concussion rules for an incident involving forward Josh Jackson in round two.

It is the first – and only – breach notice to be issued this season, however a number of clubs are still being investigated, head of football Todd Greenberg said in a statement on Tuesday.

Half of the Bulldogs’ fine will be suspended, with the club only needing to pay the extra $10,000 if there are any further breaches during the 2014 season.

Greenberg said that, overall, clubs had complied with the policy, which is aimed at protecting players who suffer head knocks during games.

“Given this is a new policy we are very pleased with the way clubs have enforced it,” Greenberg said.

“It is clear that they are taking the new rules seriously and are acting quickly to assess and treat players who suffer a head knock.”

A total of 27 players have been taken from the field to undergo the newly-introduced Sideline Concussion Assessments (SCAs) in the season’s first five rounds, with 14 of them returning to the field after being cleared of concussion.

Five clubs have been given “please explain” notices in relation to their compliance – believed to include cases involving Wests Tigers forward Liam Fulton, the Bulldogs’ James Graham, as well as Parramatta and Penrith players.

Greenberg said the controversial policy would be continually assessed, with club bosses, chief medical officers, coaches, players and the players’ union to be consulted in coming months.

“There is no doubt the new policy has raised awareness of the need to take concussion seriously,” he added.

“We know that the club doctors and medical staff are best placed to determine whether a player should return to the field after a head knock.

“We believe they are overwhelmingly acting in the best interests of their players but we will continue to take action where a breach occurs.”