[Syd Thrift]

I think it's as simple as St. Vrain threw enough pitches in his one year that the threshold thinks it's "for real". Maybe the larger issue is that the game ought to look at minor league stats with MLEs for guys like this, although even that touches on a major issue with the "major leagues" at the turn of the century: Major League Baseball was the biggest and highest league on the East Coast, the Ohio Valley, and to a degree in the Midwest, but there were even at that time vast swathes of the country where baseball was played and guys like St. Vrain were perfectly decent players who simply did not have a "major league" career because they were busy having a career in baseball in a part of the country that was unserved by Major League Baseball.

In St. Vrain's case, he was from the West Coast. Lots of guys had pretty long careers in the PCL and its predecessors, perhaps Hall of Fame level careers in some cases. Lefty O'Doul comes to mind here. I believe this is also what happened with Smead Jolley. I think MLB dipped into the South a bit more often but I'm sure there were a lot of guys who played out their careers in Texas or what have you who never touched the majors (there's a guy in the Texas League in the late 40s/early 50s IIRC who got upwards of 200 RBI in one season, for one example). And of course black players although we're getting better at acknowledging them now.

How you "fix" this is not, I don't think, as easy a question as "just make them worse". I think St. Vrain was legitimately that good at baseball. He went back down to the pre-PCL and excelled for 2 years after that before his arm started to give out. K rates tend to stabilize pretty quickly and he threw 95 innings in his one season. The issue here isn't to me so much that there is one Jimmy St. Vrain who had that one outlier season, it's that there are potentially dozens of Jimmy St. Vrains who never played in the "major leagues" for perfectly legitimate reasons.