— You wouldn’t know it to look at Eric Mangini now. But it was just three years ago that Jets owner Woody Johnson introduced the 34-year-old whiz kid as his new head coach and repeatedly mentioned Mangini's "pedigree” as if he were some dazzled horseracing mogul raving about the bloodlines of his latest purchase at the Keeneland yearling sale: "Mangini, out of Parcells, by way of Belichick?

“We’ll take him!"

Sometimes that’s the trouble with coaching trees. Some starry-eyed owner or athletic director thinks if he plucks away a top assistant who sat at the knee of a “genius” such as Bill Belichick he’ll get another Secretariat, and he ends up with some nag called WhoKnewThisGuysAStiff? instead.

In case you didn’t hear the head-banging coming from certain precincts of New England, Ohio and South Bend, Ind., the past few days, it was a lost weekend for the Belichick coaching tree. Even worse gloom seems just ahead. Football is a copycat sport, and Belichick clones could be out of vogue any minute. Expect phones to be ringing off the nightstands of all those unemployed Bill Walsh spinoffs such as Mike Holmgren, Jon Gruden and Mike Shanahan. Expect more Tony Dungy disciples to see their stock soar.

On Saturday, Belichick’s former offensive coordinator, Charlie Weis, saw his Notre Dame team lose to Top 10-ranked Pitt a week after a mortifying home loss to a Navy team, which only has the top-rated armada in the world. (Not a BCS category.)

Now many alumni want Weis fired.

On Sunday, Belichick invited wrath for choosing to go for a first down on 4th-and-2 at his own 28 with his Patriots leading the Colts by six points with 2:08 to play. New England lost, 35-34. He later said he didn’t want to punt and risk having Peyton Manning drive 70-some yards to beat him. So he chanced letting Manning have to cover only 28 yards for the game-winning touchdown if the gamble failed? 

That make any sense?

Then there’s Mangini, the Cleveland Browns embattled first-year coach. Where do we start? The 1-8 Browns are so bad, they’ll probably go off as underdogs to the wretched Detroit Lions this week. The Browns are so bad, they waited just weeks into the season to fire their first-year general manager (another import with New England bloodlines named CantGetTheDraftRight — naw, just kidding. His name was … Excuse me? He’s already in the federal witness protection program? Since when?)

And did you see the Browns’ game against the Ravens? A fan named Dawg Pound Mike tried to organize a boycott at the start of the game. Signs in the stands read “Baltimore, Can You Take This Team Too?” and “Gruden, We’re Hiring.” Then re-installed Browns quarterback Brady Quinn didn’t look anything like a pocket passer — he looked like the setter for the Pepperdine volleyball team the way the Ravens kept spiking his passes back at him. In the third quarter alone, Quinn’s first two passes were slapped down at the line of scrimmage, then two of his next three were intercepted, turning a scoreless tie into a 16-0 Ravens’ win.

Guess who Quinn played for in college?

Charlie Weis.

Guess who preceded Mangini as coach in Cleveland? Romeo Crennel, the defensive coordinator on Belichick’s three Super Bowl-winning teams who didn’t win enough with the Browns.

If you’re playing this parlor game at home, it means the Browns’ extended coaching tree is Mangini after Crennel with a long-distance contribution from Weis by way of Belichick after Belichick’s Oedipal break from Parcells in New York. (Long story. Don’t ask.)

Poor Cleveland. Is it piling on to also mention that Belichick finished a flop there, too, in his first head coaching job from 1991-95?

At least Crennel wasn’t hated. So far, neither is 33-year-old Denver coach Josh McDaniels, the latest Boy Genius to be plucked off the Belichick tree. McDaniels’ Broncos have suffered three straight losses after a 6-0 start that included him running around the field as if his copycat Belichick hoodie was on fire after his Broncos beat Belichick and the Patriots in Week 5.

For some reason, Belichick — the king of the dead-fish postgame handshake — didn’t hold it against him. He sought the kid out in the Broncos’ locker room to congratulate him.

It was a rare public grace note for Belichick.

He and Mangini and Weis tend to inspire great irritation and charges of arrogance wherever they go.

Belichick seems downright constipated when people ask him to perform normal adult functions like, you know … talk to the people. Weis got to Notre Dame and acted as if sweet-talking the alums was beneath him. Mangini’s gimmicky, hard-driving approach has left his Browns players rebelling. His tenseness and insistence on team-wide news blackouts grate on people just as it did with the Jets. One long-suffering Cleveland native, normally mild-mannered sportswriter Joe Posnanski, has blasted Mangini as the worst hire in NFL history.

You can bet Rich Kotite slept well that night.

Belichick will at least survive the recriminations he brought on himself. It seems impossible that Weis and Mangini will last.

Notre Dame’s program, which is run by a unique combination of Catholic fathers and outside Sugar Daddies, has publicly said the $18 million the school still owes Weis will not prevent firing him.

Browns owner Randy Lerner, who hired Mangini without even interviewing anyone else for the job just days after the Jets canned him, seems unlikely to make a move till after the season. But if Lerner doesn’t clip Mangini then and go shake some other coaching tree, he might want to look into a nice rental in Cabo next fall and winter. Something without DirecTV.