I don't think those two recent high-rebound games were outliers; I think that they are a sign of Krstic's potential on this team.
Maybe you're right, but this is a list of Krstic's defensive rebounds since joining the team:
0
4
3
5
1
3
11
10
1
His previous high for defensive rebounds in a game in OKC this season was 6. Therefore, I'm not ready to say that the double digit efforts are a show of his "true" ability, while his entire body of work (including 7 out of 9 games in Boston) is inaccurate.
Krstic was near the bottom of the league for defensive rebounding percentage while with the Thunder. I'd like to have more than 2 games to go on before I'm convinced that he's a good rebounder.
EDIT: For comparison's sake, Perk's defensive rebounding totals this season: 3, 8, 4, 5, 8, 8, 12, 5, 7, 4, 6, 4, 7. Average: 6.2 in 25.6 minutes.
Krstic, despite his two big games, is averaging 4.2 defensive rebounds in 27.2 minutes.