Case Play 2015-02, Will the Real F3 Please Stand Up? [Solved]

When an outfielder stands at first base in a five-man infield, what is his position called? Jim Joyce's crew had an eventful weekend (relevant: Ejections 013-017: Greg Gibson & Jim Joyce [KC]), and the rules kept on coming their way in Denver Wednesday evening. With the score tied in the bottom of the 9th inning of the Padres-Rockies game, Colorado loaded the bases with none out. To try and prevent a Coors Field walk-off (the attempt was unsuccessful...walk-off single), Padres Manager Bud Black elected to overload the right side of his infield by bringing in regular center fielder Wil Myers (F8) alongside first baseman Yonder Alonso (F3) and second baseman Yangervis Solarte (F4), creating a five-man infield while leaving left fielder Justin Upton and right fielder Matt Kemp as a two-man outfield. For his first batter, Black instructed Myers to stand next to first base and Alonso to play between Myers and Solarte, such that Myers would likely take any throw at first base.

Official Baseball Rule 1.13 allows the first baseman to wear a leather glove or mitt that is distinctly different in build than gloves allotted to any other fielder, as in Rules 1.12 (the catcher) and 1.14 (all other fielders). For simplicity's sake and the purposes of illustration in this case play, we shall refer to the first baseman's Rule 1.13 hand covering as a "mitt" and all other fielder (except catcher)'s Rule 1.14 device as a "glove."

Case Play Question 2015-02: Is "regular" F3 Alonso permitted to keep his first baseman's mitt while "regular" F8 Myers is occupying the dirt mound closest to first base, or must he trade his mitt in for a glove? Conversely, is Myers permitted to pick up a first baseman's mitt for this play?
Participation in this discussion is worth two points for UEFL owners.

Case Play Answer 2015-02: In short, yes, F3 Alonso is permitted to keep his first baseman's mitt (if certain conditions are met). Rules 1.12-14, regarding gloves and mitts, clearly indicate that only one catcher and first baseman may be in the field at any given time. In other words, regular F8 and regular F3 cannot both be considered first basemen: the positions are mutually exclusive in this regard.

Rule 2.00 defines the battery [catcher/pitcher] & infielders/outfielders, but not specifically "first baseman."

Rule 4.03(c) states that any fielder, other than pitcher and catcher, "may station himself anywhere in fair territory." This means, for instance, that a first baseman could station himself closer to second base, or anywhere else in fair territory.

Rule 10.03(a) Comment instructs scorekeepers how to handle a defensive shift: "When a player does not exchange positions with another fielder but is merely placed in a different spot for a particular batter (for example, if a second baseman goes to the outfield to form a four-man outfield, or if a third baseman moves to a position between the shortstop and second baseman), the official scorer should not list this as a new position." As such, they key phrase is "exchange [of] positions." Just as substitutions may occur "at any time the ball is dead," as in Rule 3.03, so may exchanges (known as a "change" in Rule 3.03 Comment).

In the above play F3 Alonso exchanged his mitt for a glove while Myers exchanged his glove for a mitt—in other words, they exchanged positions. How do we determine who is F3? Jeremy407 summed it up thusly, "As long as F3 has the mitt, he is officially F3." So to answer the Case Play question, F3 may keep his mitt as long as he is officially declared to be F3. If, as was the case in the accompanying video, F3 and F8 exchange mitts/gloves, then the old F8 is officially F3 for the purposes of the new play (since old F8 is now wearing the first baseman's mitt). The mitt tells us who the real F3 is; we're legal as long as only one fielder is wearing the F3 mitt at a time.

Thanks to all participants, each of whom shall receive two points for discussion of this play.

Wrap: San Diego Padres vs. Colorado Rockies, 4/22/15
Video: Daniel Descalso hits a pinch-hit game-ender with the Friars' five-man infield drawn in (COL)
Video: Black motions for Myers, getting LHP Rearick instead as gloves are exchanged (SD)