I think 4-6 weeks would be the norm. Maybe longer if there's some sort of slight tear or if you can't walk on it.

Whatever it was, he probably tried to come back too early, re-injured, and had to start over with the healing.

They also may not be disclosing something worse. Does the calf tie into some ligaments around the knee or achilles? Maybe there's something else going on too and they're only saying calf.