P(positive play) = .75*e^(-.5*((T-1)^2)), T is number of seconds Kris Joseph dribbles the ball. Pretty simple if u ask me, bet it calibrates to the data just fine.
So for example:
0 seconds: Prob = 45%, pretty good
1 seconds: Presumably gave himself some space, chance goes up: 75%
2 seconds: The exponential decline begins: back to 45%
3 seconds: 10%
5 seconds: < .1%