Years — or perhaps decades — ago, baseball magazines would have a feature in which obscure rules and unusual situations would be brought up for discussion. Bill James once described a typical question as “what happens if the live baseball lands in the pocket of a passing marsupial?” Friday night’s Tides-Indianapolis game included a play that led to a potential “knotty problem of baseball.”

In the top of the third inning, Indianapolis’ Brian Friday blooped a single to center. He was sacrificed to second by Gorkys Hernandez. Chase D’Arnaud lofted a fly ball that Tides center fielder Matt Angle misjudged. Angle drifted back on the ball, then suddenly broke out into a sprint back toward the infield and dove for the ball. From my vantage point in the seats behind home plate, I couldn’t tell whether Angle had trapped or caught the ball; and the umpire making the catch was out of my line of vision.

Friday, on second base, thought that the ball was caught and returned to second base. D’Arnaud, the batter, either thought that the ball was not caught or wasn’t sure, and he charged for second base. The two runners arrived at the same time; both dove headfirst into the base; and nearly conked heads. Angle threw the ball to the second baseman, who looked perplexed before finally tagging runners clinging to second base. Eventually, the umpire arrived, said a few words, and D’Arnaud got up and trotted to the dugout.

We still weren’t quite sure what happened. Our first guess was that Angle was ruled to have made a catch and thus D’Arnaud’s dive, though spectacular, was wasted. But our confidence was shaken when the scoreboard operators put an additional base hit on the line. After discussing this for a bit, we finally decided that Angle had not caught the ball, and that D’Arnaud was tagged out by the second baseman. By rule, if two runners are legally on a base (more on that later), the trailing runner is put out when tagged. Finally, we went back to our first opinion — that Angle caught the ball — when later in the inning the extra hit was taken off the linescore.

Now for the knotty problem. By and large, runners are not allowed to run the bases backwards. More precisely, a runner who has legally reached a base is not allowed to go back to a previous base. A century ago, a “character” named Germany Schaefer, on first base, broke for second on a hit-and-run play and stole the base successfully, although the hit-and-run failed. On the next pitch, he broke back for first base so that on the third pitch, he could try the hit-and-run again. That’s now illegal — once a player has legally reached a base safely, he can’t go back to a previous base. A runner can run back and forth during rundowns, because he’s never reached the following base — and he can return after a fly ball has been caught, because he never reached the following base legally – but once he’s reached a base, he can’t go back.

Another principle is that the final decision of the umpires is final. So, for example, if one umpire signals “No catch” on a fly ball and another umpire signals “catch”, and a runner doesn’t tag up because he sees the “no catch”, and the runner is doubled off his base, and the umpires, after conferring, rule a catch, the runner is out of luck — the final ruluing is a catch; he never tagged up; hence he’s out.

So, let’s take the Friday-D’Arnaud-Angle play and complicate it a little. Suppose that Friday reached third base. He then either saw the umpire signal “catch” or heard the coach telling him “catch” and thus returned to second base. D’Arnaud reached second base but seeing Friday returning to second, decided to return to first to allow Friday room to return. Both runners reached base safely; the umpires then declare “no catch”. Could Friday and/or D’Arnaud be then called out for running the bases backward? I don’t know the answer.