The Yankees and Orioles were both confused by the infield fly rule

NEW YORK — The terms of baseball’s infield fly rule appeared to elude both the Yankees and the Orioles on a goofy play in the bottom of the 7th inning in their opening day matchup in the Bronx on Thursday.

First, a refresher: The infield fly rule exists, essentially, to prevent defenders from intentionally dropping easy pop-ups to set up double plays. It’s in effect any time there’s a force-play situation at third base with less than two outs, and its existence makes perfect sense. Without it, a bases-loaded, no out pop-up could somewhat easily be turned into an inning-ending triple play by any defender cunning enough to let it fall in front of him. And that’d be lame.

When the infield fly rule is in effect and a batter hits an infield fly, the batter is out regardless of whether the defensive team catches the fly ball. Runners can advance at their own risk. That’s important to understand for this mess of a play:

Batter Gary Sanchez was out as soon as he hit a pop-up in front of the plate with runners on first and second and one out. But when the ball bounced off Orioles catcher Jesus Sucre’s glove, Miguel Andujar took off from first base — as if to avoid being forced out at second, which wasn’t a possibility.

But the Orioles — or some Orioles, at least — also appeared to think there was a force at second, so third baseman Rio Ruiz fired to that bag, where second baseman Jonathan Villar received it and stepped on the base instead of tagging Andujar, who was standing right next to him and would have represented the third out of the inning.

Only, since Andujar took off for second, Luke Voit left second for third, and Mullins fired the ball to shortstop Richie Martin, covering third. After a brief rundown, Mullins tagged out Voit for the actual third out of the inning.

Score it 2-5-4-6-4, or just put a big ol’ interrobang in your scorebook.