What Are The Odds That Strasburg's Debut Is A Perfect Game?

Let's put Strasburg's 90-100 pitch limit aside. If given the opportunity, in a neutral-context world, what are the odds that Strasburg throws a perfect game tonight vs. the Pirates? Outs Probability (OP) is calculated as 1-OBP. Thus, a player with a .400 OBP has a .600 OP. Calculating the OP for an NL-team for a whole game is a tricky thing, as the pitcher bats and lineup changes are more prolific per game than in AL matchups. To simply it all, I will do the following. For the Pirates non-pitcher hitters, I will use the player's actual in-season outs percentage. For the pitcher, I will use the team's cumulative average OP (.693) in my equations. Of course, all of this assumes that each player's current OP is accurately representative of their true OP level (a bold and overwhelmingly fallacious assumption; still, this is for fun and theoretical so shut up and enjoy).

Tonight's Pirates lineup (and their respective OP's) will probably look as follows:
C - Ryan Doumit (.434)
1B - Jeff Clement (.770)
2B - Ned Walker (.620)
SS - Ronny Cedeno (.714)
3B - Andy LaRoche (.692)
RF - Garrett Jones (.661)
CF - Andrew McCutchen (.619)
LF - Lastings Milledge (.678)
P (AVG OP) - Jeff Karstens (0.693)

The product of each player's OP cubed yields a theoretical and neutral context perfect game probability (or improbability) of 0.00000762%, or a little more than 50% the odds that the Indians would get perfect gamed the other night.

But who is to say a perfecto is reasonable? Too much luck involved. We all know the 20 K game is much more likely for "the next Mark Prior"...right?