Johnson said rolling substitutions would be better for player safety
England manager Martin Johnson says rugby league-style rolling replacements are needed in rugby union.
The Rugby Football Union is considering experimenting with interchanges from next season to ensure Harlequins' fake-blood scandal can never be repeated.
"Some form of rolling substitutions needs to be looked at," he said.
"I liked it when 15 guys had to battle it out and you had to be fit for 80 minutes, but you come around to thinking about it as a possibility."
The controversial proposal was one of 16 recommendations in a report drawn up by the RFU's Image Of The Game task force, which aims to restore rugby union's reputation after the blood and drugs scandals of the summer.
Johnson also said he agreed with the panel's suggestion that rolling replacements would benefit player welfare, as they would allow potential cases of concussion to be properly diagnosed.
"Player safety is an issue with players getting bangs on the head," he said.
"It needs to be looked at carefully and I am sure it will be trialled. Maybe it is inevitable."
As the rules stand, a temporary replacement is only permitted if a player has a blood injury. However, the rule was abused last season when Harlequins winger Tom Williams went off with fake blood coming from his mouth to be replaced by Nick Evans.
Johnson is concerned the existing rules can lead to a player staying on the pitch with concussion.
Phil Vickery needing a long lay-off after he suffered serious concussion in England's Six Nations win over Scotland this year, an incident which was hard to diagnose at the time.
"At the time, in the first 90 seconds, our doctor said it was difficult for him to diagnose how bad Phil was, whether he was just dazed or badly concussed," said Johnson.
"Fortunately, at the time Phil needed treatment for a cut so he could come off for a blood injury and have time to be assessed properly.
"When that was done it was obvious that no way was he going back on a rugby field that day or even for quite a while."