It's a simple concept:
OBSTRUCTION is the act of a fielder who, while not in possession of the ball and not in the act of fielding the ball, impedes the progress of any runner.
Makes sense, right? Most baseball rules make a great deal of sense.
Seriously, just watch this:
Technically, Mesoraco is entitled to the three feet on either side of the "direct line between bases", and it appears that Mesoraco was within three feet when he made contact with Indians catcher Tofu Lou Marson. Hence, obstruction.
That's the letter of the law.
But the spirit of the law? Mesoraco obviously ran directly into Marson with the express purpose of gaining the obstruction call, and thus wriggling out of the little jam in which he'd placed himself.
Essentially, he flopped. As Grant Brisbee notes, Mesoraco should have gotten a yellow card. Instead, he was awarded home plate and the Reds' ninth run.
This game's a blowout, so this won't be at all controversial. But the umpires should have some leeway to call a runner out when it's clear that he veered away from the baseline with the intent of taking advantage of a loophole in the rules.