I believe that a pick-off is supposed to go down as PK in an actual scorebook, but in virtually all box scores -including those on MLB.com- it is designated as "PO". With the broad title of the quiz and no instruction limiting to scorekeeping/scorebook abbreviations, pick off should be accepted.
In response to all the 'what abouts' for PO: while any of those can be an acronym reped by PO, put outs is a statistic that is actually recorded as PO. There are not any statistical compilations that will list pop outs, playoffs, or pitch outs as PO.
That would just be another, more advanced game. Sabermetrics, or rather, the intelligent use of sabermetrics, is the only way baseball can evolve. Baseball prides itself in its ability to confront with its own past, thanks to the insane amount of statistics ammassed since the 1850's. These stats changed and evolved through the years. I mean, strikeouts didn't become official in the NL until 1910. The hate that sabermetrics is taking from the lovers of "good ole simple baseball instincts" is as gross as the blindness of those who think that it can explain everything, from baseball to rocket science.
Can OBP be modified slightly so that "On base percentage plus slugging percentage" works for OPS? Or "OBP plus slugging" -- I couldn't figure out that I needed to just say "on base plus slugging". Great quiz.
The only possible thing I could think of for PO was pitcher only.. this is a very common thing to hear people talk about, especially in lower levels of play such as high school and college.
Very nice quiz, my favourite sport in fact, unusual for a guy from England. But it is GIDP on the MLB app and on their TV broadcasts so this one needs to be changed.
Absolutely nothing......