Cooperstown Gum Caps

In 2013 Panini put out a series of cards celebrating the enshrined members of Cooperstown in the Baseball Hall of Fame.  One of the more unique inserts they had was "gum caps" that resembled Pogs.  The front of the "cards" look like what you see above.

Many know of Pops and Goose, but not many people know of Waite Hoyt.  To be honest I had to look up his stats myself.

In looking up his stats, nothing really stood out to scream Hall of Famer.  He finished a 21 year career with 237 Wins and 182 Losses (winning percentage .566).  Over the course of 3762 innings he only struck out 1206 batters and had a 3.59 ERA.  Again, not very dominating numbers.  I thought that maybe he didn't allow many walks or hits and that's why he was elected, but his WHIP was 1.34.  By today's stats, there are a lot of guys who would be elected in the Hall of Fame if those were the standards for enshrinement.

Does anyone know what impressive stat Waite Hoyt may have to be considered one of the greatest pitchers of all time?  If so, please let me know cause I am failing to see it...