Carlton coach Brett Ratten fears the AFL's new interchange rules might mean more injuries for the game's best players.

Numerous players battled through cramp in the weekend's opening round and the Blues coach was concerned that they were made to stay out on the field.

"In the Melbourne-Sydney game there were players actually on the field getting rubbed because (coaches) want to keep players out there," Ratten told SEN radio on Monday.

"I don't know if that's good for the game."

Ratten said Adelaide's Graham Johncock was using a goal post to stretch his leg because of cramping in Saturday night's match against Hawthorn.

And he said West Coast star ruckman Dean Cox had to "virtually be pushed" onto the field in the final quarter against North Melbourne in spite of major cramping in Perth on Sunday night.

One of the AFL's aims in cutting the interchange bench was to slow the game and thereby reduce injuries.

"Hopefully none of the players get injuries, long-term ones, especially the great players of the competition," Ratten said.

"Because that's what makes it exciting for the public to go and see, the top echelon of the competition run out and display what they can do."

But AFL football operations manager Adrian Anderson stood by the league's medical advice that cutting the bench would reduce injuries.

"We have some of Australia's top medicos, who have told us that they believe that this rule will help reduce injuries overall across a season," Anderson told reporters.

"But we'll have to continue to measure that."

Anderson said it was common for players to cramp in round one.

And he said the extra fatigue helped reduce congestion around the ball late in games.

Anderson also said the new substitute rule had alleviated the unfairness created when one side lost a player to injury early in several weekend matches.

And he backed Brisbane's decision to have big man Mitch Clark return to the ground despite being noticeably groggy against Fremantle on Sunday night.

He said if a player was knocked out, they had to stay off, but if they were dazed, it was up to the club's doctor to run a concussion test, as the Lions had.

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