Old friend Eric Mangini could help the Patriots out once again Sunday if his Jets are able to rise to the occasion and defeat the Dolphins at home in East Rutherford, N.J.

The Providence Journal/ / Bob Breidenbach

It has a sort of eerie, ironic feel to it, and if you’re a Patriots fan, more than a little unseemly.

New England finds itself in the strange position of actually having to root for Eric Mangini and the New York Jets — their nemesis in the Border War, which has grown uglier in recent seasons — for its own playoff ticket to be stamped.

That’s the ironic and unseemly part.

The eerie part is that the Patriots have had their playoff fate in Brett Favre’s hands before, against the Jets no less, and it didn’t work out too well.

The bottom line for New England is this: if it can win in Buffalo on Sunday afternoon, and lest we forget, the Pats have beaten the Bills 10 straight times, and New York wins at home against Miami, then the Patriots are AFC East winners.

A Dolphins win coupled with a Baltimore loss at home to the Jaguars gets the Pats in as the sixth seed, but the disappointing Jags topping the Ravens seems much less likely.

The NFL announced yesterday that it had decided to “flex” both the Jets-Dolphins and Ravens-Jaguars games from 1 p.m. starts to 4:15 p.m. starts; that both games were moved helps the Pats.

Had the Baltimore game remained at 1 o’clock with the Patriots-Bills and both New England and the Ravens won, thus eliminating New York from contention, it’s plausible that the Jets may have rolled over and let Miami win — thus giving the Dolphins the AFC East title.

This is the same Jets team that was charged with tampering with Deion Branch, after all, and the same New York front office and coaching staff that set off the Cameragate saga last year. Given the animosity between Mangini and Bill Belichick the conspiracy theory doesn’t seem so impossible, though one would hope the New York players have enough professional pride that they wouldn’t just pack it in (the Cardinals have cornered that market anyway).

But even if the Jets go onto the field for kickoff of their regular season finale knowing that New England has won, they won’t know what’s happening with the Ravens game.

And Mangini may want the win just to save his own job, which, if rumors are to believed, he’s in danger of losing after New York spent $140 million on big-ticket free agents and traded for Favre and nose tackle Kris Jenkins and misses the postseason.

Especially since just a few weeks ago the Jets were 8-3 after upsetting the then-undefeated Titans in Tennessee and the only thing between them and an 0-4 mark this month is a bonehead play by the Bills’ J.P. Losman.

The danger for the Patriots in having the aging Favre as their potential savior is that, to borrow a line from a reader, “the old Brett Favre is not the Brett Favre of old.” It seems the magic in the gunslinger’s arm has just about run out, and even in his best years, Favre was nearly as apt to make a game-ending mistake as he was to make a game-winning completion.

In 2002, the Patriots won an exhilarating overtime game against Miami in the regular-season finale for what they thought was the division-clinching win. But the 12-win, Favre-quarterbacked Green Bay Packers didn’t put up much of a fight against the Jets, and New York’s win led to New England being knocked out of the postseason and unable to defend its first Super Bowl title.

One of the well-worn mantras around Gillette Stadium is “do your job,” and perhaps that phrase has never been trotted out more often that it has in recent days and weeks by New England’s players and coaching staff.

All the Patriots can do is win — they’ve known since their loss to the Steelers at the end of November that they’d have to run the table to give themselves the best chance to play in January, and thus far, that’s what they’ve done.

They’re playing their best football of the season, as Matt Cassel continues to improve, the run game has its full complement of players to grind out yards in hard winter turf, and the defense is using some industrial-strength concealer to hide its biggest flaws.

All they can do is their job, which is to go into Buffalo and grab a victory from the not-dead-yet Bills.

And then root for Favre and the Jets, which is eerie and unseemly all at the same time.

smanza@projo.com