NFL

Manningham’s improvement fueled by hard work

THERE is a wonderful tale that has traveled around the NBA the past few years, illustrating how Gilbert Arenas propelled himself from an invisible member of the league’s draft class of 2001 to one of the most-productive — and highest-paid — guards in the league (whenever his health isn’t betraying him, anyway).

For hours on end after he was completely bypassed in the first round, for years afterward, Arenas would shoot, alone, in gymnasiums, and every time he would drop 25-footers, every time he would perfect his one-on-one moves, he would utter a name — “Joseph Forte!” “Brandon Armstrong!” “Jamaal Tinsley!”– that was selected before the Warriors took Arenas with the second pick of the second round, one ahead of the long-forgotten Omar Cook.

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“I’m not being a jerk when I do that,” Arenas told the Washington Post a few years ago. “I’m reminding myself when I do that, not anyone else. But if those guys happen to see what I’m doing . . . well, that’s OK, too.”

You wonder how many times the names of the 13 wide receivers picked ahead of Mario Manningham in the 2008 NFL draft have similarly scrolled across Manningham’s brain the past two years. Manningham was one of those players even non-fans used to track when he was playing at Michigan, a YouTube regular who always seemed to reserve his best stuff for high-profile games against Notre Dame or Penn State.

Yet for all that charisma, name after name of receivers known only to Mel Kiper kept filling the draft board that April afternoon in 2008. Some — Donnie Avery, DeSean Jackson, Eddie Royal — have already proven themselves legit. Yet there were others — Dexter Jackson? Limas Sweed? Jerome Simpson? — that had to cut right through Manningham’s soul. Had he really fallen that far?

The truth is, he had. His 40 times were stunningly slow. He admitted to marijuana use. He reportedly did awful on the Wonderlic test. And even his own coaches and teammates at Michigan whispered that the gap between potential and production was gallingly wide.

So he fell to the defending champion Giants in the third round, and when he did he heard GM Jerry Reese offer what can often be a kiss-of-death analysis by saying, “Talent-wise, I think the guy could have really gone in the first-round,” and he had to hear his new no-nonsense coach, Tom Coughlin, warn, “He can be a successful player in this league. But that could be taken away very, very quickly,” and then he spent most of 2008 watching, playing only seven games, catching all of four passes.

This is where he reached a critical fork in the road. There are a lot of rookies with potential who become ex-players by year two. Manningham could have gone that way. Instead, he did something else: He picked up his cell phone. He started texting Eli Manning like mad, asking how he could improve, letting the quarterback know he wanted to become his new wing man. And he backed up the earnestness with hard work.

“He made himself into an important part of this team,” Tom Coughlin said.

Just how important was on full display Sunday for Giants Nation to enjoy and the rest of the country to observe, Manningham catching 10 balls for 150 yards, showing he has lost none of his in-game flair, either. On a touchdown catch late in the half he made a Lynn Swann-esque grab by reeling the ball in on his back after it drizzled off his fingers, and on the climactic drive late in the fourth quarter he gathered in a tipped ball on third down that officially planted the Giants in field-goal range.

“People are going to say what they’re going to say,” he said afterward, speaking of the Giants’ much-maligned receiving corps when he could really have been talking about his own interesting rise to professional prominence. “I have a job to do and there’s nothing more important than that.”

Though if Early Doucet, Harry Douglas and Malcolm Kelly — to name three of 13 — wanted to pay attention, perhaps that wouldn’t be such a terrible thing, either.

michael.vaccaro@nypost.com