Although there is no event at the Combine that can directly gauge a player's will to win, it still manifests in his performance on the field. And as long as the stats reflect what actually transpires between the sidelines, they capture the effects of the competitors’ intangible qualities. And if the intangibles don’t show up in the numbers, then they didn’t matter in the first place.
What statistics can’t do is separate the physical-material tangible qualities, such as speed, strength and skill, from the intangible ones. They are captured together. But that's no different than trying to separate the effect of speed from the effect of strength. All qualities, whether tangible or intangible, are inseparable using game statistics alone.
If a great player is also a great leader who inspires his teammates to play better, then that will be reflected in his teams’ statistics. It may not be captured in his personal stats, but that has always been true of the effects of teammates on each other’s performance, whether tangible or intangible.
There are exceptions, usually temporary. If a team is one win from the playoffs, and their opponents have been eliminated from contention for weeks, then the team stats to-date won’t fully reflect the relative motivation of each team. But once the game is done, the game stats will reflect the difference in motivation, assuming it matters.
Don’t get me wrong. I’m in favor of good character and the will to win as much as the next guy. But to the extent these qualities influence play on the field, the numbers will capture their effect. So the next time your buddy says stats don’t measure the intangibles, you can say, ‘Sure they do. And besides, where have these magical qualities been hiding all season? And why haven’t they shown up on the field until now anyway?’