Pass breakups is a commonly accepted stat. Anytime a defender knocks the ball away from the receiver it is a pass break up. Interceptions are obvious. The Big 12 refers to these together as passes defended. Last year Peavy was 9th on this stat.
I was under the impression that the 26 Career Plays on the Ball in PFF's stat did not mean that he didn't allow a reception, rather that of the 26 that were incomplete, he intercepted five and broke up 21? Not allowing a single reception over three years would be a far more impressive stat (in my mind anyway.)