Now this, hockey fans, is how to do a third-period rally

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Patric Hornqvist somehow winds up atop the Stars' Antti Niemi. - MATT SUNDAY / DKPS

Four times already this NHL season, these Penguins have rallied in the third period to prevail, with three of those overcoming multiple-goal deficits. And they've done so, seemingly, with the flip of a switch.

Which is really impressive, of course.

Until it isn't.

Because the caution flag with comebacks is that they're almost always accompanied by a whole lot of luck. And when that luck inevitably flips its own switch, the formula is exposed as fatally flawed.

Think Brooklyn, for example.