Leading sports doctor Dr Peter Larkins has called for the AFL to consider adding a fifth man to the bench as a concussion substitute.

The debate over the negative impact clubs experience when they lose players to concussion was raised over the weekend after the Swans lost Jake Lloyd less than a minute into their match against Hawthorn to a head knock, while Sam Reid did not return after half-time after a strong tackle by Shaun Burgoyne.

The AFL and clubs have strengthened their concussion protocols in recent years, whether that be on game day or in terms of matches missed.

There had been a concussion substitute between 2011 and 2015 but that was removed when the interchange cap was cut from 120 to 90 with four active players on the bench, having been three on the bench plus a substitute.

Larkins, who first raised the issue on 3AW, said the return to a substitute specifically for game-ending head knocks would have several implications but it needed to be considered.

"We have been very, very strict on concussion management on the day in the AFL, which is great," he said.

"But as a result of this heightened threshold of awareness, it means that even (a player with) the most mild concussion is excluded for the rest of the day, even though they might technically be fine 10 minutes later, 15 minutes later, like we used to see in past times.

"I am not suggesting we go back to past times by any means but I am just saying it's different when you have got a broken ankle, ripped hamstring. Clearly, that person is not fit to return on the day. I guess we are really having a specific medical approach to head (knocks) and concussion.

"In the event that a player is excluded very early in the game because of concussion, and if you have two ... it's a topic of discussion. In the sense of fairness and balance in the competition, should we looking at having a dedicated sub concussion player - not just a sub player."

North Melbourne was the only other club to lose a player to concussion on the weekend, with Trent Dumont hurt in the second half against Carlton.

In a column with Fairfax Media, former West Coast and Carlton great Chris Judd questions whether a substitute would be open to tactical exploitation.

Larkins admitted the concussion substitute could be open to manipulation, and realised some would question why a substitute would be restricted to a head knock.

"The question is - you could have two hamstring (injuries) in the first quarter. Should there be a benefit given to those clubs?" he said.

"That's why I acknowledge that it's tricky. I am just making the point that concussion has become such a big component of excluding people from games. I can't think of a weekend where we haven't had a concussion so far in 10 weeks."

The AFL says the merits of a concussion substitute have not been discussed.