When the late Steve Belichick heard others refer to his son as a genius, he would sometimes wonder why they’d attach that label to a football coach, a man who stalked up and down sidelines for a living.

Steve may have been trying to protect his son — the word genius carries with it a certain weight — but if Bill Belichick can get his New England Patriots into the postseason this year, his status as a genius, even if only of the football kind, will certainly be cemented.

Think back to 1:21 p.m. on Sept. 7, the moment that Tom Brady crumpled to the turf at Gillette Stadium, screaming from the pain in his left knee. As Brady limped off the field, the hopes that New England would build on the remarkable success of last season, one that fell just moments short of history, left with him.

At least that’s the way it seemed.

Brady had been so durable, and his presence under center was the one constant the Patriots had. New England had dealt with its share of injuries before and overcome them. Down a cornerback or two? Let’s try Troy Brown at the nickel. Have a no-name receivers group? Not an issue with Brady throwing to them.

In all of those situations, Brady could still play, and that was all that mattered. He knew how to win games, whether in thr rain or in the sun, with Randy Moss and Wes Welker in the huddle with him or with Reche Caldwell and Doug Gabriel.

But in Brady’s stead stepped a quarterback for whom the term “green” was an understatement. Sure, Matt Cassel had been on the roster in New England for more than three years, but he was a backup in every sense of the word.

Right?

When Brady was injured, it wasn’t just the Patriots’ playoff hopes that went down with him. Those who were loath to call Belichick a genius began rubbing their hands together in breathless anticipation. Let’s see how great the genius is now without his all-world quarterback, they squawked, trotting out Belichick’s record without Brady (decidedly under .500) and with him (substantially better).

A funny thing happened on the way to the demise of the New England Patriots’ dynasty, however.

It turns out that Bill Belichick can actually coach a little.

Truth be told, if the playoffs started today, New England would not be a participant. The team is in second place in the AFC East, and Baltimore and Indianapolis would claim the wildcard berths.

But the playoffs are a month away, and the Patriots’ fate is still in their own hands. And that is a remarkable thing.

If New England is one of the six AFC teams still standing on Dec. 29, the day after the final day of the regular season, it will probably be because Belichick has outdone himself.

Losing heart and soul Rodney Harrison six games into the season would have been tough enough. But being without Asante Samuel and Randall Gay and patching together a cornerback group composed largely of veteran castoffs and rookies posed its own challenge. Seeing three of the five running backs they retained at the start of the season miss games to injury and putting the ball in the hands of an undrafted rookie was unsettling.

And now there’s the linebacker dilemma. Perilously thin at the position, New England has turned to two players who haven’t played a down in the NFL this season, one of whom is 43 days from his 40th birthday.

Each of those things, on its own, might have done in other teams. Throw in a devastating injury to the franchise quarterback a mere 20 snaps into the season, and most other clubs probably would have packed it in.

Not New England, though.

Cassel went from feel-good story/game manager to overnight star/game-winning quarterback. He’s not terribly flashy, but he’s consistent, and that’s just as good.

The running game has kept rolling right along, totaling better than 120 yards in each of the last five games and five of the last six.

The secondary is still a soft spot, but the Belichick system is all about using strengths to cover weaknesses.

When they kick off today against the Seahawks, the Patriots know they more than likely have to run the table in their remaining games to get into the postseason, and if they do that, in this most improbable of seasons, it will be a stroke of genius.

Even for a man who stalks up and down the sidelines of a football field for a living.

smanza@projo.com