I saw the Mets play the Padres on Friday, and something strange happened. I’d always thought a run that scored on an inning-ending play only counted if the third out had been made on a tag. A force out means no run, right? Wrong.

Get this: in the first inning, Dillon Gee walked the first batter, Will Venable, and got the next one out on a pop-up before giving up a single to Yonder Alonso that moved Venable to third. Then, with runners on the corners and one out, Jesus Guzman hit a shot that looked to be an easy double off the wall, that is, assuming it didn’t clear the fence. Mike Baxter put an end to all that by making the incredible catch you see above before doubling Alonso up at first. Here’s the video.

Venable had crossed the plate before they made the third out, but so what? It was on a force, the run didn’t count, or so I, along with most everyone in the stadium, thought. That “everyone” includes the Mets’ first baseman, Ike Davis, who told the AP, “I gave a first pump because I thought the run wouldn’t count.”

But alas, Ike and I have something in common: we were wrong. Well, that and the fact that we’re both hitting under .200 this year. Then again, I haven’t had 156 at bats (hint: I haven’t had any). Anyway, we both thought the run would be nullified by the double play. It was not, because as is the case with so many of baseball’s finer points, the devil is in the details.

Remember when I told you it was wrong to think a force out means no run? Well, I was lying. See, it’s not that this play was an exception to the rule, that the run counted despite being a force out. Rather, it’s that the second out on a tag up double play like this one isn’t actually a force out. Why, you ask? Well, that requires some definitions. To the rule book, let’s go!

Alright Robin, now that we’ve got our atomic batteries to power and our turbines to speed, I’ll tell you. Rule 2.00 of the Official Baseball Rules states that a force play is one in which “a runner legally loses his right to occupy a base by reason of the batter becoming a runner.” Likewise, Rule 7.08 tell us that “if a following runner is put out on a force play, the force is removed and the runner must be tagged to be put out,” and Rule 7.10(a) states “Any runner shall be called out, on appeal, when after a fly ball is caught, he fails to retouch his original base before he or his original base is tagged.”

So what happened on Friday is this: the force on Alonso was removed when Baxter made that catch, and the third out, which came from the ball getting to first before he could tag up, was technically a tag out. That’s despite it looking so much like a force play.

Funny, isn’t it? Because the definition of a force out is so specific, that of a tag out is the opposite. A tag out doesn’t actually require a runner being tagged with the ball, a base can be “tagged” as well. So basically, a tag out is anything that isn’t a force out. But hey, it’s these little complexities that make baseball so great. It’s one thing for me or Ike Davis to be surprised, we’ve only got 40 years of baseball-watching between us, max. But it’s entirely another that my grandfather, who was there as well, can learn something new about the game he loves after seeing it played for over 75 years. In baseball, there actually is something new under the sun, and that’s what makes it such a beautiful game.