The Substitute Rule in Cricket: From a 60-Year-Old Test to the IPL Impact Player

On the morning of the second day of the India-Australia Test at Bombay in the 2026-65 season, Norm O'Neill's stomach began to hurt. The pain started just after play began. Australia batted first, so O'Neill's Test was over before he ever took the field for fielding. One batsman out of action in whites, eleven Indian players inside the ground. In that moment, the biggest gap in cricket's rulebook became visible. I began with a Rangpur blog and ended up drawing Russia's midfield geometry. Along that road I learned one lesson that applies equally to cricket, football, and esports. If you do not understand the rule that shapes the game's structure, you will misread the result too. The 2026-65 Bombay Test is the clearest example of that lesson. The question there was not who played better. The question was what a team could do when a player was lost to the rules. The answer was almost nothing. Under the rules of the time, a substitute fielder could be brought on, but only for fielding. That substitute could not bat and could not bowl. Since O'Neill never batted, no replacement could bat in his place. Australia therefore played two innings with ten batsmen, and kept India in check with eleven fielders. The asymmetry is not equal. The batting loss is irreparable, the fielding loss can be covered by a substitute fielder. While analysing this question, I stopped at one number. In the 1960s, touring squads typically travelled to India with fifteen to sixteen players. Among them there was practically no Test-quality reserve batsman. So when one player fell ill, the impact was far greater than in an equivalent situation today. Today squads carry eighteen, plus travelling reserves. Then, one absence struck directly at the spine of the batting order. In my view, this incident is not really a story about rules, it is a story about medical infrastructure and touring load. Bombay's October heat and humidity, the travel arrangements and medical support of that era, these three together made a touring player's stomach illness not an accident but an institutional risk. O'Neill did not just miss one match, his entire tour was at risk. This kind of event was not unusual at the time. Now let me step back. Cricket's Laws are framed by the Marylebone Cricket Club, while the Playing Conditions are set by the ICC. The difference between these two layers is the most important thing here. In 2026 a change came to the Laws, permitting the use of a substitute wicket-keeper. This was a rare liberalisation. Before that, if a team lost its wicket-keeper, a non-specialist player had to keep for the entire innings. This change removed that old distortion, and it carries no obvious vector for abuse. But the story does not end here. Under cricket's Laws a substitute cannot bat or bowl, yet under specific Playing Conditions it is possible. Concussion substitutes and Covid-19 replacements fall under this exception. These two kinds of substitute get full rights, that is, they can both bat and bowl. This is where the most subtle point of the analysis lies hidden. The rule kept to preserve the balance of the contest has become the most usable, and therefore most abusable, rule of all. I want to make one thing clear here. Cricket has two distinct words that ordinary fans often confuse. One is substitute, a replacement fielder with no batting or bowling rights. The other is replacement, with full rights. In 2026-65, O'Neill was the first kind of case, a player lost with no replacement available. Today's concussion substitute is the second kind. Without understanding this distinction, any discussion of cricket's substitution rules will go in the wrong direction. This two-tier arrangement has an obvious consequence. The team with greater batting depth, that is, one carrying an extra batsman of equal standard, benefits most from the concussion substitute. Nobody intended that advantage. It emerged on its own. As a result, a new incentive has been born in team construction, one that effectively rewards batting depth. Selectors may not even think about it consciously, but that is how the structure works. Let me move from here to the IPL. In the 2000s the ICC introduced the Supersub in one-day cricket. A few years later it was withdrawn. The reason was clear. In a fifty-over match, adding an extra batting slot distorts the balance between bat and ball across the whole innings. The market value of all-rounders also fell. Resistance from coaches and players was fierce. Years later the same idea returned, but in different packaging. The BCCI launched it as the Impact Player in the IPL. In a twenty-over match, extra batting depth means more boundaries, more advertising time, more excitement. So a rule that failed at international level succeeded at league level. The difference is not in the rule, it is in the format and in who owns it. I do not see this as mere curiosity. To me it is a product-design lesson. The same rule damages the balance of the contest in international cricket, yet increases the density of entertainment in a franchise league. Because a league's goal is not the balance of the contest, it is audience pull. Leagues have therefore become a kind of laboratory for the ICC. New rules are tested commercially first, and may or may not arrive at international level later. One thing is worth remembering in this context. A player can play under two contradictory rule sets in the same season. In the IPL he takes the field as a twelfth player, while in an international match that opportunity does not exist. Cricket has now accepted this duality. But for the analyst it matters. To measure a team's strength, reading the Laws alone will not do, the Playing Conditions must be read too. There is another fine rule I cite repeatedly. If a bowler is injured mid-innings, another player can come on to complete that over. This rule exists in no other major sport. The reason is structural. An over is a legal unit that must be completed. So the Laws must nominate a substitute bowler mid-over. Here it is not fairness but the structure of the rule that decides the outcome. Putting all this together, I arrive at one conclusion. The 2026-65 Bombay Test is not merely an old incident. It is a clean natural experiment. It shows how badly one player's illness can hurt when no rule exists. Today's concussion substitute and Covid replacement were created precisely to reduce that harm. But every solution brings new risk with it. Because the rule that helps one player opens a door for abuse by another. The question now is this. In the coming days, will cricket appoint independent doctors to verify concussion-substitute eligibility, or will it trust teams' own judgement? Watching from Rangpur, the answer to this question will decide how credible Test cricket remains over the next decade. Let me add one more fact. The biggest change in the history of cricket substitutes came in 2026, when concussion substitutes were permitted in Test cricket. The opportunity was first used at the Lord's Ashes Test. Since then the rule has been used in multiple matches. Lawmakers have become flexible over time, that is acknowledged. But drawing the line between flexibility and looseness is difficult. Finally, one last thought. Reading cricket's rulebook, I notice the same thing again and again. Rules are written to meet the needs of one era, and later those same rules create the problems of a new era. O'Neill in 2026-65 was a victim of the old rules. Today's Impact Player is the answer to those old rules. Six decades in between, and what cricket learned about substitution in those six decades is this: if the structure is not right, talent is not enough.