kenpom has them as the worst team in the league, and the worst defensive team in the league. Defensively they are definitely not a pressure team as they don't get steals, they don't force TOs, and they don't block shots at a high pace. Teams also generally shoot pretty well against them and overall they have been very poor, giving up a high eFG% and a high 3PT%.
However, the key in their 3 best wins (OSU, MU, and UT) is that the opponents shot poorly overall, but expecially from behind the arc. OSU shot 5-25 (20%), MU shot 5-21 (23.8%) and UT shot 5-18 (27.8%). I have no idea how much of this was due to their defense and how much was due to a poor shooting night from the opponents, probably a bit of both.
A few other stats of interest; a) it appears Capel has taken the SLTH philosophy on offensive boards in that the Sooners are below average in that area. They are also a fairly low-paced team at 67 per. b) Another interesting aspect will be drawing fouls, the Cats are #1 in the country at it, and OU is top 20 in not allowing teams to go to the FT line. c) They are also solid, but not great, at not allowing offensive rebounds.