I never "root" for an athlete to get injured.
However, from a gambling standpoint, a key injury forces the market to adjust on the fly, giving bettors who know the product to gain an advantage.
My favorite injury in college basketball was Luke Harangody of Notre Dame.
I believed he was grossly overrated and I was able to cash a few bets after he went down with an injury during his junior season in South Bend.
I knew he was an accumulator (gaining points and rebounds from ND's offensive schemes) and I also knew the Fighting Irish had players off the bench who could serve as capable replacements.