Mostly it's the people he coaches who failed to perform well, with a few notable exceptions like Erod and Workman .
Also Brian Bannister needs to be questioned as to the lack of development in the minor league system. None of the guys brought up this year showed pitching maturity, , command, control and big upside. Some like D Herndez's LH fastball and as soon as it can be located somewhere in the strike zone he could be good.
The best that can be said for the young pitchers in 2019 is that they got exposure and experience at the MLB level, so they know better how to approach 2020 ST.