I think games played is a poor metric to measure eligibility. Instead it should be minutes played.
And I think 26 is too old. Shouldn't be older than 25 when the season starts.
Calder eligibility rules don't even bother defining a "professional league".
In terms of "major professional league", the way the Calder is awarded, that basically just means "the NHL", and I'm fine with that for this purpose.
To be fair, I thought the cut-off was 25 as well, so I'm fine with going with that as the cut-off as well.
In terms of the games played, I find it difficult to think of anyone as a "prospect" if they've played in over a third of the games in the regular season.
Really, though, any threshold is arbitrary. I'm fine with using the NHL's arbitrary metric here, because otherwise, we end up arguing every single time we do these lists about who should count or not.