Trevor Bauer has been loudly stating that the Astros' pitchers are using foreign substances on the ball to get the tremendous spin rates that they do. McCullers throwing 24 straight curveballs might in fact be suspicious.
I feel like the game tolerates some bending of the rules so long as the techniques were available and used in the 1920s--tar or earwax or whatever on the ball, a certain amount of incorrect calls from the umpire, and so on.
[0] https://www.newyorker.com/sports/sporting-scene/baseballs-st...