We don’t just expect our NFL coaches to win every season they walk the sideline. We now expect them to keep winning long after they’ve retired.

Of all the expectations, roles and honors we hang on NFL coaches — strategic genius, master motivator, surrogate father — one of the most peculiar, and most pervasive, is the idea of the “coaching tree.” It branches off — sorry — from the concept of coach-as-patriarch, holding that a truly brilliant coach’s ideas take root — sorry, again — in the minds of his many assistants, blooming — look, there’s a reason this is a metaphor — on NFL sidelines for many seasons to come.

This year’s playoffs feature two living legends of the headset in Bill Belichick and Andy Reid. Both can trace their lineage back to two of the most famous coaching trees in NFL history; Reid to Bill Walsh (via Mike Holmgren) and Belichick to Bill Parcells. And both have inspired an entire forest of current and future head coaches.

View photos Bill Belichick and Andy Reid have impressive coaching trees, but whose is the best? (Getty) More

Let’s take a look at those coaching trees, shall we? You never know what surprises you might find when peering in amongst the branches.

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You know Belichick’s mantra: “Do your job,” a maxim covered in a thick, glowering crust. He’s got a coaching tree that, with the exception of the Detroit Lions, extends throughout the AFC. They range from long-timers like Romeo Crennel and Eric Mangini to younger proteges like Matt Patricia and (at some point again soon) Josh McDaniels.

Most of Belichick’s disciples try to emulate Belichick’s gruff, sour exterior, none with more success — both on the field and the sideline — than his onetime, short-term assistant Nick Saban. (The entirety of Saban’s vast success has come in the college ranks, so it doesn’t apply to the NFL merits of Belichick’s coaching tree.) Belichick has created a widely imitated, but rarely duplicated, template for how a coach should view the world around him. (As an enemy.)

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Andy Reid’s coaching tree is like water to a fish: you don’t realize it exists because it’s so pervasive. Though Reid himself has struggled in the postseason, the men he has inspired, and the ones they have in turn mentored, have gone on to substantial January success. John Harbaugh leads that charge, but literally half a dozen current NFL head coaches owe a debt of gratitude to Reid.

While Reid gets plenty of grief for his clock management during games, it’s clear that he has forged a legacy that’ll last long after his own career hits all zeroes, no matter how many timeouts he still has left.

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Take a look at this. Disciples of Reid and Belichick have coached 18 of the league’s 32 teams. That’s an impressive reach, and it speaks to both the validity of these coaches’ philosophy and, well … the inherent conservatism of the NFL hiring establishment.

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