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Undrafted rookie running back BenJarvus Green-Ellis is now a starter for the New England Patriots.

Posted by ESPN.com's Tim Graham

FOXBOROUGH, Mass. -- BenJarvus Green-Ellis remembers picking up his No. 2 pencil and filling out those standardized test forms, one letter per slot where students are supposed to write in their names.

There was never enough room to accommodate nine letters for his first name, 10 letters and a hyphen for his surname.

"I always ran out of space ever since I was small," Green-Ellis said. "They put more space on those now. But my last name never will fit."

All that matters these days is that Green-Ellis fits nicely on the nameplate across the shoulders of his New England Patriots jersey.

Green-Ellis, known by his teammates as "The Firm" because he sounds like a four-partner LLP, is the latest interchangeable part the Patriots have inserted into a lineup that has kept them atop the AFC East.

Undrafted out of Mississippi and unable to make the team out of training camp, the quiet rookie emerged from the practice squad last month with a mouthful of a name and became a handful for defenses to contain.

Green-Ellis has taken over the Patriots' injury-ravaged backfield and enters Thursday night's game against the New York Jets on quite a roll.

"You have to play an eight-man front to stop him," said Ed Orgeron, who coached Green-Ellis at Ole Miss and now coaches the New Orleans Saints defensive line. "He breaks through tackles. He knifes through shoulders. He has tremendous running ability to get the short yardage and break through tackles."

Green-Ellis has scored a touchdown in four straight games and is coming off his first 100-yard performance in Sunday's 20-10 victory over the Buffalo Bills.

He will face a challenge against Jets nose tackle Kris Jenkins and the NFL's fifth-ranked run defense, but Green-Ellis isn't running like some fifth-string flunky.

"For him to step up the way that he did when we had some injuries at the running back position was great for us and spectacular," Patriots quarterback Matt Cassel said. "He did a great job and he continues to do a great job.

"I think he's really earned a spot on this team with the way he's performed and continues to perform week in and week out."

That Green-Ellis is playing on Sundays is partially attributed to the misfortune of others. Several running backs had to get hurt before the Patriots summoned him from their taxi squad Oct. 11.

Laurence Maroney is done for the season because of a shoulder injury. LaMont Jordan likely will miss his sixth consecutive game with a calf problem. Sammy Morris has missed three games with a knee injury, and his availability against the Jets is listed as questionable.

Green-Ellis starts with veteran Kevin Faulk providing relief.

"If certain things hadn't happened, BenJarvus might not have gotten the opportunity," Patriots coach Bill Belichick said. "That's been true of other players in other years in other situations. Sometimes those opportunities didn't come as quickly. Sometimes they did -- like [Tom] Brady.

"The most important thing for the player is to always be prepared. You never know when those chances are going to come, but when they do come, be ready to take advantage of them and really make something of it. If not, somebody else is going to get it."

Almost as surprising as Green-Ellis' contributions to the first-place Patriots is the fact he wasn't drafted.

Green-Ellis began his college career at Indiana and immediately showed he belonged in the Big Ten. He ran for 938 yards and seven touchdowns as a freshman, 794 yards and five touchdowns as a sophomore.

The New Orleans native transferred to Ole Miss to be closer to home. Green-Ellis red-shirted in 2005 and then became only the second player in school history to rush for 1,000 yards in back-to-back seasons.

He performed at an elite level in arguably two of the nation's three most competitive conferences.

"I figured he would get a chance to get on a team and make it," Orgeron said. "He had a lot of success in college. I thought he was a great back. He had shown me he could do it."

Green-Ellis' measurements at the NFL scouting combine were pedestrian. He ran the 40-yard dash is 4.6 seconds. He had a 30 1/2-inch vertical. Scouts didn't like the way he caught the ball. There was concern he carried the ball 920 times in college and might've been tattered.

Twenty-three running backs, including some late-round flyers from such schools as Toledo and Northwest Missouri State and Montana, had their names called at the draft.

Green-Ellis wasn't among them. He belonged to nobody.

"He's a great football player, but he might not wow you at the combine, running around and jumping," his agent, Roosevelt Barnes, said. "But there are some players, when they put the pads on, they can play, period. Ben is that type of player."

Barnes said a dozen teams showed interest in signing Green-Ellis as a free agent. Barnes claimed the Cleveland Browns wanted him badly. The Kansas City Chiefs, San Diego Chargers and San Francisco 49ers courted him, too.

Barnes steered Green-Ellis toward the Patriots because of their track record as a meritocracy.

"He just needed an opportunity," Barnes said. "Down the road I think he has the chance to be a Pro Bowl caliber player.

"He's not going to be flashy. He's going to be like Curtis Martin. At the end of the day, you're going to say 'Man, he had 100 yards. Can you believe that?' That's how Curtis Martin was. That's BenJarvus."

Even taking Barnes' bias into account, the NFL always will find room for a player with anything close to that ability.

As the weeks go by, fan mail is starting to pile up in Green-Ellis' locker. The general theme of the notes and autograph requests indicate folks simply like the ring of his name.

"People," Green-Ellis said, "just tend to take a liking to it."

For the record, his mother's name is Latonia Green. She tacked on his father's surname when BenJarvus was in middle school. BenJarvus came about simply because Latonia Green liked the way it sounds.

But when it comes to signing an autograph, Green-Ellis admits it can be tough. There's only so much surface space on most items.

But, just as there's only so much room on an NFL roster, Green-Ellis finds a way to make it work.

"I shorten it up, BJGE, four letters," he said. "When I was in college I used to sign my whole name, but it took too long. That's one of the things the Mississippi [sports information department] came up with.

"I've just been rolling with it ever since."

Patriots' unheralded gems
Player How acquired The skinny

WR Troy Brown Draft, eighth round, 1993 When injuries raked the secondary in 2004, Brown filled in admirably.
QB Tom Brady Draft, sixth round, 2000 The consummate unheralded replacement-turned-star, he stepped in for -- and then made everybody forget -- Drew Bledsoe.
G Stephen Neal Undrafted, 2001 College wrestler signed as a project but eventually took over starting spot from Joe Andruzzi in 2004 and has been a regular when healthy.
C Dan Koppen Draft, fifth round, 2003 When Pro Bowler Damien Woody went down, Koppen stepped in as a rookie and has been the starter ever since.
QB Matt Cassel Draft, seventh round, 2005 Brady comparisons are increasing by the week.
RB BenJarvus Green-Ellis Undrafted, 2008 From rock-bottom on the depth chart to 100-yard rusher.

Jets-Patriots, BenJarvus Green-Ellis, Matt Cassel, Tom Brady, Laurence Maroney, LaMont Jordan, Sammy