Doctor is full of it as far as stretching goes. Warmup yes. Don't sprint all out when leaving the parking lot. Spin high cadence for a mile or two. If you have to climb immediately, use low gears and spin. Don't stand. Keep the muscle loading in your legs down for the first 15 minutes as much as you can. You'll have a lot more endurance if you warm up slowly in the very early portion of your ride. I learned this when I was 10. On group rides, a good leader will take care of this for you.

The other thing you can do is to strengthen your calves. Hard to believe you could blow a calf on a bicycle. When they heal up, start doing 1 set of standing one-legged calf raises on a stair, full range of motion, twice a week. Once they strengthen a bit, do them to complete exhaustion. Hurts like the devil, but only for a little while.