Offline I never have an issue but online there is no rhyme or reason I can find to consistently warm up a pitcher correctly. I have even selected ready and waiting with a pitcher who was a sliver away from being full and he comes in already in the yellow and had full energy to start.
Stretch and toss will have guys fully warmed up.
It's always without fail too when it happens that pitcher is about useless for his mandatory 3 batters.
That's what irritates me. I don't know if it's just me but when you select ready and waiting, they don't stop warming up. I brought someone in last night and it immediately said he was out of energy. But you can't switch him until he throws to 3 batters.