Posted: 21/03/2014 at 15:08
Overstress the calf before it's fully healed and you risk a worse tear and not being able to start your marathon, let alone complete it. Listen to your physio.
It is possible to complete a marathon off a longest run of 15 miles. Not ideal and definitely makes it harder and slower but do-able. I have actually completed a marathon off a longest run of 12 miles but definitely wouldn't recommend it; there was a lot of walking involved and it hurt a lot
You've said yourself that the last 20 miler would be a confidence booster so start working on the positve mental attitude and telling yourself that you can and will do it.