It is a week now since I had the problem with my calf muscle. I have been resting this week (no exercise at all) and I thought it was getting better but yesterday I jumped down from a 1 foot high plinth onto the ground and there was a big twinge. Clearly is in not yet fixed.
I was hoping to start tennis again this week but that now looks in doubt. I may need to get some advice from a physio this week.