Former England captain Michael Vaughan said substitutes who replace injured players in the first innings of a test match should be able to bat and bowl for the remainder of the contest instead of being restricted to fielding duties.
Under the current laws of the game, injured players can be replaced during a match but the substitute is only allowed to field, with the lone exception being a concussion substitute.
The restriction leaves teams shorthanded with only 10 eligible batters and puts added strain on a bowling corps if the injury was to a bowler.
Zimbabwe's frontline seamer Richard Ngarava could bowl only nine overs before being helped off the field due to a back injury on the opening day of their one-off test against England on Thursday.
England's top three batters then feasted on Zimbabwe's pedestrian attack, with each of them smashing a hundred as the hosts racked up 498-3.
"Injury replacements should be permitted in test cricket in the first innings of the game," Vaughan told BBC Sport.
"If there's a genuine injury in the first innings, it affects the game and the entertainment, which fans pay money to watch. The first innings is a good cut-off to make it fair."
Former Zimbabwe seamer Henry Olonga said substitutes should be allowed to bat or bowl regardless of when they enter a match.
"I'm open to the idea of substitutes, perhaps with a limited number, but not necessarily like-for-like and not only restricted to injuries," the 48-year-old said.
"If you want to grow the game globally, then make it more like other sports where subs are allowed.
"Think of football, tactically if a game is going in a certain way, substitutes can be used to tweak the direction."
The Marylebone Cricket Club (MCC), the custodian of cricket's laws, did not immediately respond to a Reuters request for comment.