Monday morning, I came across this tweet:

Fly ball into the LF corner at Wrigley Field, but who is the kid sticking his head out the door?! farm5.static.flickr.com/4006/452658673…

— Stirrups Now! (@uniformcritic) July 16, 2012

Go ahead and look at the photo.

After some detective work, I think I've figured the exact date on which it was snapped. That, and an explanation of who the kid is, after the jump.

There are actually quite a number of clues as to the year this photo was taken. Obviously, it's Wrigley Field in Chicago, but also, the hairstyles and clothing of the fans date it to the late 1960s or early 1970s.

Then there's the uniform. The numbering style shown was used by only one National League team in that era -- the Houston Astros. This is confirmed by the small star on the stirrup, also worn only by the Astros.

So who is this player? There are four men who played outfield in that era for Houston who wore No. 22: Jesus Alou, Nate Colbert, Jose Herrera and Ron Davis. The player in the photo is clearly Caucasian -- that eliminates everyone except Davis.

Ron Davis played left field for the Astros at Wrigley Field exactly four times, all in 1967. On two of those dates, the baseball-reference boxscores say it was cloudy -- you can clearly see the sun shining, so that narrows it down to two. And of those remaining two, there's only one in which a Cubs hitter hit a double to left field -- the second game of a doubleheader on June 25, 1967, which would also match up with the shadows creeping across left field; the double was hit by Ted Savage in the seventh inning.

Oh, yes. The kid? He was probably a clubhouse assistant or bat boy. Before 1984, when they put the clubhouse behind the third-base dugout, the Cubs' locker room was located through the door shown in the photo; the team would walk across the field into the clubhouse after games.