Great thread with lots of good information! I just experienced this injury on Monday, 4 days ago, and while I've had some improvement doing just RICE + Advil, I still can't push off with that foot while walking without pain.
Even though this happened in March, it was around 70 degrees at the time we were playing and I wasn't hydrating as much as I normally do as my opponent barely even slowed down on side changes. After playing two long sets, the very first point of the 3rd I attempted to push off quickly to get to a short second serve and felt a pop in my calf. I think I actually heard something pop too but that might've been my imagination. Immediately afterward I could barely stand on that leg but now if I move slowly enough I don't limp but I wouldn't dream of trying to walk fast or run.
At least I've learned my lesson about hydration and I won't let an opponent dictate how long I spending drinking during changeovers after this.
I agree completely that hydration plays a part in this injury, that has not been stressed enough in this thread.