Yep.
Fitness is a cop out. That's not to say it's (obviously) not fundamentally important, but it's (more often than not) not the key reason teams struggle.
Execution x talent wins football games.
Execution plays into defence just as much as attack. It's a jammer being covered on the sweep, it's the centre making the correct read, it's harmonious connection between the entire edge, it's a unified line both during the set and on kick-chase, it's diffusing the vast majority of kicks, it's a blocker or escort not missing their assignment, it's knowing when to pressure playmakers and when to hold off, it's being effective at first contact, it's controlling the player on the way to ground effectively in order to get your markers and defensive line set etc.
And in attack, it's the obvious stuff. Be better connected, take your chances, make sure passes stick, decoys hitting side shoulders, etc., all that good stuff we know. But it includes discipline as you mentioned.
The fittest teams can fail to execute and go longer without it affecting the game as much. But the best teams tilt the game in their favour through execution on both sides of the ball and rarely need to dig deep in order to stay in the game. It seemed a weekly occurrence from us.
All NRL preseasons do a sufficient job at preparing their players for the rigours of the season-proper. Then, once we're 6-8 rounds in, match fitness takes over and teams (not individuals) are largely congruent in their overall fitness levels.
If that wasn't the case, we would expect to see teams who have no ball and are run ragged in the early rounds, start to dominate from a fitness perspective as the season wears on, simply due to the fact that they'd have been asked to do so much more in-game work than other sides, therefore improving their fitness.
But we don't.
Execution x talent wins football games.
