To sub, or not to sub?

Ponder for a moment an alternative conclusion to the Adelaide Test, one that arrives after both teams are able to call on substitutes to maintain a full complement of 11 fit players. Jacques Kallis and James Pattinson still limp off with injuries incurred while bowling, but instead of remaining on the scoreboard they are replaced - Kallis by Ryan McLaren and Pattinson by Mitchell Starc. The addition of fresh bowlers alters the course of the match.

McLaren's bustling medium-fast follows up from Kallis' initial breakthroughs, and also reduces the role played by a profligate Imran Tahir, to restrict Australia to a slimmer first innings - Michael Clarke drags McLaren onto the stumps having made a mere 147. Thus chasing a reduced target, South Africa entertain as many thoughts of winning as survival until Starc delivers a swerving spell with the second new ball midway through the final day, dismissing McLaren among three victims in as many overs.

Starc's left-arm footmarks also create more purchase for Nathan Lyon, who finds sharp spin and variable bounce out of the rough to ensure South Africa are bowled out with an hour and a little more than 100 runs to spare. Kallis, meanwhile, is passed fit for the Perth Test, and Pattinson's recovery period is revised to give him a chance of playing against Sri Lanka at the MCG on Boxing Day.

Such a scenario will be outlandish to some and anathema to others, but with every glimpse of a batsman grimacing in pain at the crease and every camera shot of a bowler limping from the field, the radical concept of allowing substitutes in Test cricket slips closer to the realm of the possible. Whether that is also the realm of the necessary still depends on one's point of view. Medical practitioners and physios around the Australian game are at the vanguard of global lobbyists for the concept, while players and coaches are softening in their resistance - bowlers moreso than batsmen.

Older cricketers, and captains, are reluctant to tamper with the venerable and venerated concept of 11 versus 11, irrespective of injuries, conditions or the changing tactical fashions of other sports. Paul Marsh, the Australian Cricketers Association chief executive, spoke for many of his members when he stated that any such change would "tear at the fabric of the game". Following the Adelaide Test, South Africa's captain Graeme Smith spoke warmly from this perspective about the respect engendered among combatants for playing the last game that leaves nowhere to hide for five days.

"I think that's the whole challenge of Test cricket really," Smith said. "When you watch Peter Siddle bowl at the end of his tether in the last 12-18 balls of the day to someone who's batted all day, that's what Test cricket is all about. I don't think there's a sport out there that really tests you for as long mentally, emotionally and skill-wise other than Test cricket, and I think maybe rules like that might soften the blow a bit. That's why people who look back over time can be proud of what they've achieved, that they've been able to handle what this game is all about."

Smith's views are emblematic of the opposition to any concept of substitutes. Nonetheless, the views of medical men are creeping towards wider acceptance, albeit slowly. The concept of a cricketer being subbed out of a first-class match is already in place under exceptional circumstances in Australia, as Ricky Ponting and numerous New South Wales-based team-mates for Australia were replaced in Sheffield Shield matches to avoid injury and a scheduling clash ahead of the first Test in Brisbane. Ponting's hamstring was deemed too tight for him to complete a match for Tasmania against South Australia in Hobart, while Michael Clarke and Mitchell Starc played only three days of four at Allan Border Field so they could join the rest of the squad at the Gabba.

This year, Cricket Australia's playing conditions committee - of which Marsh is a member - agreed in principle to the use of a single substitute for either injury or tactical reasons in Shield fixtures. It was viewed as a radical step at CA, and ultimately too radical at the ICC's headquarters in Dubai, from which word filtered back to Jolimont that enforcing such a law would risk the first-class status of the Shield. That edict killed the concept for the 2012-13 summer, but a serious discussion on it is evidence of progress in the mind of the Cricket New South Wales team doctor and sometime Australian team medical officer John Orchard, among the most vocal advocates of the change.

"I think everyone who's in the preparation and injury side of looking after cricketers is unanimously in favour of it, and we're getting much better penetration into the cricket part of the structure - there are now a significant number of coaches and even players who are in favour," Orchard told ESPNcricinfo. "It wouldn't have even been on the agenda five years ago and now there are people lobbying on the cricket side, not just the injury side."

The central plank of Orchard's argument for substitutes in Test matches is that it must be seen as a natural counterbalance to the wildly contrasting demands now placed on international cricketers via the poles of Test matches and Twenty20 fixtures. In terms of training, preparation, and execution they are as divergent as a marathon and a sprint, creating a chasm between formats down which increasing numbers of players are falling with injuries.

"In the days when you only had one major form of the day, the matches were spaced out nicely and you could treat Test cricket as a marathon and train like a marathon runner, bowl lots of long spells in the nets and lots of long spells in Test cricket," Orchard said. "It was a sport which didn't have many injuries. But the ask of the modern player, which is to come out like a sprinter in T20 and bowl four overs of smoke, two days' rest then another four overs, and then adjust from that to the marathon efforts of bowling 40 overs in Test cricket with maybe only week or 10 days' break in between, bodies all over the world are having a problem with that.

"It's not that one country's got poor injury management and poor physios and poor doctors, it's just that the human body's not designed to do that. We've suddenly entered a high-injury era for cricket, where every country has got players playing T20 and Test cricket, and in no country are the bowlers standing up and coping well with it. You can try your preparation in all sorts of ways, but that adjustment is becoming very different to make."

There are numerous variations on what form the substitutes system might take. The concept of replacing a player only when injured appears flawed and open to exploitation, as rugby has discovered with its blood rule. A single substitute available across the course of the match, essentially a 12th man freed up to play, is the most measured option, already debated by CA and advocated by the likes of the Victorian coach Greg Shipperd. Orchard's suggestion is the most far-fetched, allowing bowlers to be subbed out once they have reached a certain number of overs, in the manner of baseball pitchers.

"If cricket joined other sports and embraced substitutions you could make cricket a little bit closer to T20 cricket," Orchard said. "If you had players who could bowl 15 overs in an innings in Test cricket and then get subbed out and bring in a fresh bowler, it would be a radical change but it would be in response to another radical change, which is T20 cricket. When T20 was first suggested and played it was considered a bit of a joke, hit and giggle, now it is treated very seriously and it is here to stay.

"You certainly are getting some old-school people in cricket saying we should limit T20 because it is ruining Test cricket, and in one sense they're correct but in another they're out of date. No one is going to limit T20 cricket when it is getting bigger crowds and it's bringing in more money than the traditional forms of the game. You're never going to stop players playing in tournaments that earn more money than their Test cricket.

"Bringing subs in is a radical solution, but it is one that has to be debated more and more. It is really a matter of how long we're prepared to sit back and watch injuries have a greater and greater impact on cricket matches, before people get sick of outcomes of Test matches being decided by who happens to have the least injuries rather than who has the better side."

The sight of the injured combatant fighting through pain and physical restriction to do his best for his team is among sport's most compelling, but it is a drama that invariably leads to a long delay until that player may return to action for the sequel. Kallis' efforts with the bat in Adelaide have more than likely ruined his chances of playing in Perth, while Pattinson's team-oriented inclination to try to keep bowling after he first felt pain, ignoring it until he could barely breathe, is likely to have lengthened his rehabilitation time by a significant amount.

"If changes are made to allow subs, people will miss the innings of your Jacques Kallis coming on and playing with a hammy and in obvious pain," Orchard said. "That's great to watch in terms of human courage, and some of the most famous innings over the years have been batsmen under duress, and that is something you would miss if you brought in subs.

"But on the other hand we have Pat Cummins have his debut [in Johannesburg last year], get injured and play through with the injury, help win the Test match in a great display of courage, but we're now behind the ledger in terms of how much cricket he's missed with injury since then, opposed to how great it was to watch him in that Test. We're missing him more going forward for the fact he played through in that Test."

Ultimately, the possibility of substitutes in Test matches will rise or fall based on the views of the players themselves. They are the most vocal advocates for Test cricket itself, and if they begin to lose interest in its physical risks and psychological demands then change may not be long in coming. Australia's captain Michael Clarke offered a carefully divergent view from Smith, stating that international cricket had become far more of a squad game. Even though he loves the breadth of the challenge posed by a Test match, Clarke is a little less wedded to the concept of 11 v 11.

"To me it's such a hard game, it's Test cricket, it's the pinnacle, the hardest game in the world, the greatest game in the world," Clarke said. "There's going to be injuries, especially when you have to work as hard as both teams have had to work over the first two Test matches of this series, but you've got to find a way.

"We look forward to a third Test with maybe some new faces on both sides. International cricket is not just about 11 players, it's about a squad. That's why Australia's been so successful for a long period, because of the strength of first-class cricket in Australia, players manage to come into the team and have success. [11 versus 11] is how it is, so I accept it."