By Tony Massarotti

Bill Belichick has been called a genius and a mastermind. And this is apparently how he wants it: New England at Denver for the right to go to the Super Bowl, a still-thriving Tom Brady against a rapidly fading Peyton Manning for the AFC Championship.

On paper, the Patriots should win this game.

If they don’t, we’ll be left to second-guess the decision-making that put them in this position.

Don’t look now, Patriots fans, but your team blew it. Even after losing at Denver in Week 12, New England had the inside track to the top seed in the AFC. Then the Pats went out and gave up a 14-0 lead against the Philadelphia Eagles, at home, thanks, at least in part, to a downright stupid onside dropkick by Patriot and former rugby player Nate Ebner. Shortly thereafter, Belichick’s team mismanaged the clock and forced itself into a punt that was blocked and returned for a touchdown, opening the door for a stunning succession of plays that triggered a Philadelphia win.

The real sin in that game? Playing without Julian Edelman and Rob Gronkowski, Belichick aggressively coached as if he had both. A week later, New England simplified its approach and dumbed down its offense, winning at Houston by a 27-6 score.

By then, clearly, Belichick had recognized his mistake.

But it wasn’t his last.

When the Patriots went to New York in Week 16, the Patriots needed one win in its final two games to secure the top spot in the AFC. Still without Edelman, the Patriots played the Jets into overtime, then won the coin toss. Belichick made the curious decision to kick, on a day when the weather was no factor, despite possessing arguably the greatest quarterback (Tom Brady) in NFL history.

So what happened? The Jets promptly went down the field and scored a touchdown, depriving Brady of the chance to even step onto the field in overtime. Most New England fans didn’t really sweat the outcome, believing the Patriots would win in Week 17, at Miami, against a bad Dolphins team that checked out weeks earlier.

By that point, if one wanted to argue that New England’s health was more important that home-field advantage, you had a case. Despite earlier reports that Edelman might be back for Week 17 — he had begun practicing — the Patriots sat him out. Gronkowski was similarly used conservatively. New England did not even attempt to get the ball to anyone other than a running back for its first 20 snaps of the game — the large majority of those were runs — which nonetheless seemed curious for a team that threw more passes than all but four teams in the league.

Why Brady was in the game at all is anybody’s guess.

Here’s the point: most national analysts have chalked up New England’s late-season problems to injuries, which is only partly true. Yes, over a stunning succession of weeks, New England lost left tackle Nate Solder, running back Dion Lewis, Gronkowski, Edelman, wide receiver Danny Amendola, linebacker Dont’a Hightower and linebacker Jamie Collins, among others, to injuries. And yet, if the Patriots had won just one of three games against Philadelphia, the Jets and Miami, New England would still possess the top spot in the AFC, meaning they would be hosting the Broncos this week instead of playing at Denver.

Will that matter? Time will tell. The same voices defending Belichick now are, of course, the ones who champion his coaching when the Patriots overcome injuries. For whatever its worth, home teams in the conference championship games are 64-34. Brady is a mere 2-6 at Denver and has lost his only two playoff appearances there, and the tandem of Brady-Belichick is 0-2 against Peyton Manning when on the road for the AFC title game.

Admittedly, this is not the same Manning. Again, by Week 17, the Patriots had little choice but to get healthy, something proved in the divisional round of the playoffs against Kansas City. But the bottom line is that the Patriots should have been able to get healthy and preserve home-field advantage throughout the playoffs. Instead they stumbled down the stretch to give Denver a fighting chance.

And they stumbled, lest there be any doubt, because their coach — who remains the greatest of his era and arguably the greatest in the history of the game — got careless, a little too loose, maybe even a little sloppy.

Tony Massarotti is an avid Boston sports fan and has covered sports in Boston for more than 15 years for both the Boston Herald and Boston Globe. He now serves as a co-host on afternoon drive on 98.5 The Sports Hub in Boston. He was a two-time Massachusetts Sportswriter of the Year as voted by his peers and has written four books, including “Big Papi,” the New York Times-bestselling memoirs of David Ortiz. You can follow Tony @tonymassarotti.

Tony Massarotti