But expecting them to not lose any players for any part of the season is the whole issue (and a ludicrous proposition). Every single team loses rotation players or a starting player for parts of the whole season (the facts show they have actually been really lucky with respect to injuries).
You're right that you've got to factor injuries into any win prediction for a team.
I think two things are relevant and true here:
(1) Jarrett Jack was disproportionately important for that team because you need something approaching average point guard play to avoid being horrible in today's league, and he was the only guy on the roster who could give them that for 30+ minutes a night.
(2) Jarrett Jack was one of the healthiest guys in the NBA over the last 3-4 years. He barely ever misses time. So it's unlikely that many were predicting him to miss much time, let alone the last 2/3 of the season.
Most of the talk all along that I saw was aimed at Lopez's ankles / foot. He's just gotta go down! He'll definitely miss time! That hasn't happened, and he's been the main reason they've been competitive in a number of games this season. Lopez is a beast when healthy, and he's been healthy.
You can go both ways with this. I appreciate your humorous point about your aunt having balls, but predicting that a team will be bad because you're "sure" that they'll lose certain key guys to injuries for large portions of the season approaches magical thinking / faith beyond a certain point, too.
They could have lost, say, Andrea Bargnani and Wayne Ellington to season ending injuries instead, and it might not have affected their win total that much. Injuries are to a large extent random, so placing too much emphasis on that when you're trying to predict what will happen with a team doesn't make much sense to me.
My tack has always been to err on the conservative side, which in this case meant assuming the Nets would enjoy relatively good health for their main guys, because, well, when was the last time the Celts had good luck with this sort of thing?