calf stretching problems

Hi, I was playing handball professionally for a long time. I had very good career until I got injured. During a very important match while I was trying to shoot on opponent team's goal my Achilles tendon break up. Pain was enormous and I have to pause for more than six months. Now almost 15 years after that I still feel pain in my leg and when I stretch my calf I feel pain too. I would like to know are there some different ways to stretch my calf but to avoid a pain?

Hi, my friend who was tennis player also injured his calf and he was trying to find way how to stretch it without pain. It may be useful for you or at least maybe it may give you some idea how to avoid a pain. He used to stand on the edge of stairs and let his weight to pull him down while he was on his feet toes. He was holding for something by his hands and regulated weight which was stretching his calf.
Sometimes he used to do it in the swimming pool standing on the ladders and it was also helpful.