calf/achilles

does anyone know the difference between say a torn calf (gastro or soleous (sp)) and like achilles tendonitis? what are the symptoms? tennis players anyone? is it possible to "play through the pain" with tendonitis in the achilles, and where does that typically occur on the leg for a tennis player/runner? anybody? heh, i just called myself a 'tennis player.'

almost finished with paul yoon's book, that's coming soon.