Sherman's game has never been based on speed. He's always been a little slow, in fact. He's a phenomenal corner because of what he has between the ears. He reads the play, and puts himself into position to break it up.
A partial tear is a conundrum, and I hope Dissly gets the surgery. Partial tears never seem to heal quite right, and reinjury is a huge concern. Sherman had partial tear(s), and knew it was just a matter of time before he went down. If Dissly doesn't get the surgery, he will be in the same boat, looking at the very real possibility of losing another season to injury. I really hope he doesn't try the "conservative" treatment option of letting it heal.
Yes, Achilles surgery and recovery sucks. Yes, it is risky, and getting it "just right" still requires some measure of luck. But, if he doesn't get the surgery, I bet he goes down, mid-season, with a full tear.
JMHO.