For whatever reason HBD doesn't show negative numbers, so if the actual current stamina is below zero this cycle and next, it just shows as 0 (0). Your best bet is to deactivate these tired pitchers, promote some MiLB guys to fill out the HiA and above teams, and /or sign dudes from tryout camp. damag has it exactly right--you will need multiple SPs in the minors per level because they just don't have the stamina to last. Since you can just activate / deactivate players, it's not that big of a deal.