For those seemingly unaware, even before you consider the advantage that having more top class players than many opponents, here is why just having a bigger squad gives you an advantage.
1. Practice. Smaller squad, when injuries occur you don't have enough players to have pack v pack scrums and lineouts. You can fit other players in but the contest is not the same & often not possible. Similar for opposed back sessions. More players; more productive sessions
2. Dirt trackers - when you need 'cannon fodder' to hold tackle bags/shields, take hits in tackle practice, act as bodies to be cleared out at breakdowns, you can use non-star players - this lessens the chance of starting players being injured.
3. Rest - star players can rest during training sessions, whilst opponents are having to make their best players work more often. Less rest - more injuries; less sharpness over a long season.
Games - you can absent players from match squads so they get physical & mental rest.
Games - you can absent players from match squads so they get physical & mental rest.
4. Competition - if your squad stays fit you have fewer positions in which there is no proper competition. The benefit of this is self-evident to anyone who has worked within a squad.
5. Injuries - with bigger squads there is less pressure to bring back players, star and 'ordinary' and you don't have to risk playing someone in a crucial, or any, game until they are fully fit.
You can scan match-day lineups and say breaching the salary cap had no difference, but you can't be certain it would have been the same if the club had a smaller squad because you can't tell what effect injuries would have had. You also have to factor in the advantages listed.
