If Billups did tear his Achilles, he is not just done for the season, his career is in jeopardy.
I blew my Achilles at a 24 year old and it took over a year to get healthy and able to play basketball at 80% of what I was prior to the injury.
Chauncy is much older and I would not be surprised if he retires.
Achilles Tears are one of the worst injuries for tall men, you cannot put any weight on the leg for 6 months and then you have to rehab with an atrophied leg that takes up to another 6 months. I tell ya, its a horrible injury, I dont wish it on anyone.