Just a quick note on what's happening here to non-baseball people. I don't know about the translation but what the douche director is saying about Goro's speed from "Set" is that Goro is using a "slide step" technique. When runners are on base, pitchers often ditch their big leg kicks during windup and quickly shift their weight forward when throwing to avoid giving the baserunners time to steal. Often, this is very jarring for the pitcher, ESPECIALLY young pitchers like Goro, and it causes a loss speed and control. It's why Sengoku hooked his home run foul, Goro's pitch was slower than he was expecting so he swung early and hit it too far to the right.
You can see an example here with Chicago White Sox (Now Chicago Cub) pitcher Jose Quintana:
What Toshi is saying is "Go back to your full windup, I'll stop anyone from trying to steal home plate."