One letter effectively asks why a certain player was not replaced during a game.

The second letter, pointing to another incident in the same game, asks why a certain player was replaced.

The letters focus on the vexed issue of concussion and its abuse under the free interchange rule where concussed players are allowed to be substituted without affecting the number of replacements permitted.

So, the first letter identifies a player who the NRL's chief medical officer, Dr Paul Bloomfield, believes showed symptoms of concussion but was not replaced, an offence that attracts a $20,000 fine.

The second letter, also following the review of match, is usually prompted by NRL general manager of competitions and operations, Nathan McGuirk. He questions whether a player who "failed" a concussion test did so because his team was close to its maximum number of interchanges and needed a certain type of player on the field.

This NRL communication with clubs does demonstrate that headquarters treats concussion seriously but identifying it can be a very subjective science.

Former Newcastle Knights representative winger, James McManus, is suing his club for not exercising a duty of care to a concussed player.

McManus' legal action won't overcome the NRL's major obstacle in confronting concussion: the player.

Often over-looked in this debate is the passion players have to play.

Look down to the sideline when a player is replaced, whether by the coach in the course of play, or for a concussion test by the club doctor.

If a symptom of concussion is irrationality, you'll see it on the bench.

Players, such as the Storm's former representatives, Dallas Johnson and Ryan Hoffman, have been known to scream abuse at the football manager, demanding to be sent back on the field.

Some are so furious (often seeking revenge on the opposition player who caused the concussion), they do not hear a single word from anyone, football manager or club doctor.

The least co-operative person in the confusing mayhem can be the player.

There are also strategic problems with replacing a player suspected of being concussed.

On almost all occasions when a player is seen to be wobbling, dazed, or even lying on the ground, his team is defending.

Assuming the referee does not stop the game, the responsibility is on the trainer to escort the player to the sideline, aware this will leave a gap in the defensive line.

It's much easier when the team is in attack. The ball carrier, or captain, can simply stop play and point the referee in the direction of his distressed teammate.

Most NRL clubs follow concussion protocols conscientiously and don't hesitate to have a player checked on the sideline by the doctor who asks him a series of questions.

Coaches suspect the computer test, taken at the first training session to assess whether the player is eligible to be selected for the next match, can be manipulated by a player desperate to keep his place in the team.

In the long run, as players, coaches, administrators and even club doctors learn more about concussion, the most effective deterrent will be the game itself.

If a grand final can be lost because a concussed player missed a tackle on an opponent who scored the winning try, it will be taken seriously.

But the passion of those who play is as old as the game itself, a point made by a guy I met recently.

It concerned a game of touch football played at Wangi Park on Lake Macquarie, near the big power station.

It was the late 1970s and three boys, best mates, had just finished Year 12. Two of them were very talented five-eighths and opposing captains on the two touch football teams. The third boy, the source of my story, was, in his words, "useless".

"I was fit but horribly uncoordinated," he said. "The first ball passed to me, I dropped."

Each captain chose a team member in order, a humiliating but continuing practice with touch football games today.

"But when it came to me, neither of my best mates wanted me on his team," the guy recalled.

A furious fist fight ensued. "They had to be pulled apart. They were so competitive, each wanted the other to have me," he recalled.

"We were best mates. Like brothers. But they were fighting over not wanting me.

"It sums up the passion we had for the game.

"I wouldn't have had me on the team, either."