I thought Mayer and Anthony were better opening day choices, but KC had been tearing up the minors at every level. To me, they all looked ready- more ready than Narvaez, Early, Tolle and Dobbins- other rookies that ended up doing well.
This is not an easy choice to make, and I'm not sure we can easily say out organizational player development assessment protocol is flawed, because one guy slumped badly after his first 20 games or so. The reason all these guys didn't get an immediate show was the vest already in place.
Yes, Mayer could have been chosen over KC at 2B, but I think they wanted him to play more games and play at SS, because Story was still a big question mark, if not just on his health questions. Anthony doesn't play 2B, and we can already see how his great start has forced the trade Duran issue to the forefront. Narvaez got his shot, in part because Wong got hurt. Dobbins, Tolle and Early were not really expected to play in the bigs. They made it by injury attrition.
I totally agree that the experience gained by these rookies, some just brief stints has enormous value to them and the club. There aren't as many looking to break into the bigs, next season, except maybe Perales or limited roles by Sandlin or Romero. (Romero will not be on the 40.)
We still have more to learn about KC, namely his position, and Jh Garcia. We need to see how Mayer can hit lefties, and how strong his arm looks after the wrist injury. We'd like to see if Anthony's power can increase, and how he looks on defense over a full season. We'd like to see if 2025 was a fluke for Narvaez, Some of us want to see Tolle and Early get plenty of starts in the bigs, and maybe some want them on the opening day roster. It was good they got a taste of the bigs without any harm to their egos.
If Campbell is to be set up for LF, I'm not sure there is room for Jh Garcia, perhaps even if Duran is traded. I wonder if DH is the best spot for KC, but we have Masa and maybe Casas as the DH, the latter for sure if we sign Alonso or another 1Bman. (Alonso might also be a DH type.)