Hi therapist101
Some sports physio out there night have some better ideas. However here are a few things that come to mind:
Have you had a look through this systematic review:
PEDro - Detailed Search Results
It does outline a few other techniques other than eccentric training with some evidence to consider.
Have you had it definitively diagnosed by and ultrasound? If not it might be worth doing this to be sure the diagnosis is right and if it is right to also look at the extent of diseased tendon. There are of course a number of related pathologies that may need checking out.
What about other kinesiopathological problems - have you had the balance between your lower limb muscles checked out. Could the achilles tendons be taking the brunt in your sprinting due to a muscle imbalance problem or motor control issue. What about any issues with the posture of the foot - eg pronated hindfeet?
the last thing might be worth considering - do you think you may now have a chronic pain component to the problem - so where the pain you are experiencing is disproportionate to the problem. If this is so taking a pain management approach might help.