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New England Patriots running back Dion Lewis seemingly has emerged from crumb rubber, musket smoke and pixie dust, so we are inclined to chalk him up to mystery.

How else can we explain an undersized running back leading the NFL's best offense in rushing yards after being cut twice and sitting out of football for almost all of last season?

A mystery this is.

But every mystery has clues, if you know where to look and who to talk to. This week, Bleacher Report has tracked down many of the people with insight into Lewis' past and progress to figure out just how he has arrived as such a surprising force in the Patriots' backfield.

Clue No. 1: Lewis had shown extraordinary talent in the past

In the fall of 2008, there were rumors on the campus of the University of Pittsburgh. LeSean "Shady" McCoy, the team's star running back, might leave school early and apply for the NFL draft. If he did, the Panthers were going to need a replacement who could step in the following season, and they didn't have one on the roster.

Dave Wannstedt, then the head coach, gave his assistants an assignment: Find a running back who could start for the team next year.

Jeff Hafley, the secondary coach, was in charge of recruiting New Jersey. He placed a DVD on Wannstedt's desk of a running back from Blair Academy.

He needed to explain something, though. "Coach, he's only 5'5", 180," Hafley said, almost apologetically. That was why Lewis was not being heavily recruited by others. He would be offered scholarships from just two other schools, Miami of Ohio and Tulane.

Wannstedt watched the DVD anyway. After just eight plays, he hit the stop button on his remote control.

"Get him in here," Wannstedt said. "If he is the type of person we want, we will offer him a scholarship."

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Lewis replaced McCoy the following year, breaking McCoy's record for most points by a Pitt freshman and breaking Tony Dorsett's record for most rushing yards by a freshman in the Big East.

It did not take long to see Lewis had special talent.

"Barry Sanders was the quickest I ever saw in terms of making a guy miss in a hole," Wannstedt said. "Dion isn't Barry Sanders, but he had some of that same make-a-guy-miss-in-a hole quickness. Plus he had 4.5 speed to outrun you. He could catch. He did things you can't coach."

Lewis was about more than just quick feet. Buddy Morris, the strength coach for Pitt at the time, gave his players a test that measured pound-for-pound strength. Morris said Lewis bench-pressed twice his body weight and squatted more than 500 pounds, making him the strongest pound-for-pound player on the team.

Clue No. 2: There was a reason many overlooked Lewis

At the 2011 scouting combine, Lewis measured 5'7" and weighed 193 pounds. Those numbers spoke loudly to NFL ears. Despite his stats at Pitt, including once carrying the ball 47 times in a single game, Lewis would not be considered durable enough to be an every-down NFL back.

Lewis' small frame did not diminish the enthusiasm of Joe Banner, then the president of the Eagles. The loudest voice in the Philadelphia draft room pushing for the team to select Lewis was Banner's. But even he had tempered expectations. He thought Lewis would be a change-of-pace back in the NFL. The Eagles subsequently targeted Lewis as a fifth-round pick, and they were pleased to select him there.

"There is a prejudice in the NFL against smaller players, and for good reason," said Banner, now an ESPN analyst. "Most smaller players don't overcome the size challenge. But that stereotypical thinking cost a lot of teams a chance at a guy with a lot of talent. He is a good example of that."

Smaller running backs almost always are backups in the NFL. And most coaches want backups to have special teams value. Lewis has not been a return man, and he isn't big enough to block or play coverage on special teams.

Lewis understands his lack of size has cost him opportunities.

"Some people might not want a smaller back on their team, but I don't think of it that way," he said. "I've always been one of the smaller guys on my team, my whole life, so I'm used to it. I knew what I wanted to do and I wasn't going to let anybody tell me I couldn't do something."

Clue No. 3: Lewis was held back by circumstance

Lewis just wasn't in the right place at the right time early in his career.

The Eagles weren't right. Lewis' arrival in Philadelphia coincided with McCoy's arrival as a premier back. In 2011, Lewis' rookie season, McCoy led the NFL in touchdowns and was voted First Team All-Pro. He took 73 percent of the running back touches that year.

"When Dion had opportunities, he was outstanding," said Marty Mornhinweg, who was the Eagles offensive coordinator. "But he was behind LeSean."

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The following season, Lewis stayed behind McCoy and fell behind two rookies—Bryce Brown, who checked in at 5'11", 223, and Chris Polk, who was 5'11", 222. It did not help that Banner, who had been Lewis' football godfather, had been phased out in Philadelphia.

Banner went from Philadelphia to Cleveland, and one of his first moves was to call the Eagles to ask if they would trade Lewis. Banner acquired Lewis a second time in a deal for linebacker Emmanuel Acho.

The Browns weren't right, either. Lewis appeared to be on the verge of breaking out in Cleveland the summer of 2013. Then he fractured his fibula in the second preseason game.

"I would say he was going to play a great deal if he had not been injured," said Norv Turner, who was the Browns offensive coordinator that year. "After [the Browns traded] Trent Richardson [in September], Dion would have definitely been the starter."

Instead, Lewis spent the season on injured reserve. He came back in the summer of 2014, but most of the people who had traded for him were gone. In camp, Lewis did not look like the same player he was before the injury, and the Browns' new regime prioritized size in the backfield. Lewis was cut as the Browns elected to retain Terrance West, Isaiah Crowell and Ben Tate, each of whom stood 5'11" and none of whom weighed less than 220.

The Colts weren't right. They picked up Lewis one week into the season. The plan was to develop a specific role for him and work him into the offense. Many coaches see him as the type of player who is best utilized in a specific package. But days later, the Colts lost defensive tackle Art Jones to an ankle injury. They needed a roster spot to replace him, so Lewis was let go.

The Colts will get their first look at him since last September on Sunday when the Patriots come to town.

After Lewis was cut, the Giants and Patriots had him visit for workouts. Neither team needed a running back at the time. Both were interested in signing him down the road, after the season.

Lewis checked the transaction wire dutifully and made frequent calls to his agent, J.R. Rickert, to assess the landscape. But as far as NFL teams were concerned, Lewis was either too small, not durable enough or not capable of being plugged into their system.

Clue No. 4: Lewis changed the way he trained

After last season ended, Lewis came to a realization. Whatever he had been doing in the past in terms of training and preparation was not enough. So he spent six weeks at the Fischer Institute in Phoenix working harder and smarter than he ever had.

With bands, boxes, medicine balls and sleds, he worked on acceleration, deceleration and agility for functional running back movements.

Lewis was surrounded by others with similar goals. His college roommate, Jon Baldwin, accompanied him, and they became roommates again in Arizona. Others who were regulars at the Fischer Institute included Aaron Dobson, Logan Ryan, Julio Jones and Tyrann Mathieu.

Chip Gosewisch, the sports performance director at the Fischer Institute, said Lewis was "aggressively focused" on preparing himself for this season. "When he put his cleats on to do the agility drills, there wasn't any rest," he said. "He didn't go through anything less than 100 percent. He wasn't ever going through the motions."

Lewis came to realize how precious an opportunity can be. "He won't forget when he was sitting on the couch," Rickert said.

Last year was not easy, but Lewis is better for having survived it. "I was discouraged a little bit through the process, not getting picked up," Lewis said. "But I kept my head held high and worked hard so I could make the most of my opportunity when I got one."

Those who know him well say Lewis appears to be playing with more explosion than before. "I feel stronger," Lewis said. "I think I got better at everything."

Clue No. 5: The situation was finally right

It became apparent very quickly that Lewis fit perfectly in the Patriots' offensive puzzle. Before the team took a single snap this season, Tom Brady told NBC broadcasters Al Michaels and Cris Collinsworth that Lewis would become a cult hero in New England. Three games into the season, the Patriots signed Lewis to a two-year contract extension that reportedly includes $1.8 million in incentives.

Lewis has been nicknamed "Jitterbug" by teammate Julian Edelman. Cowboys defenders Barry Church, Jack Crawford, J.J. Wilcox and Corey White understand why after each whiffed on Lewis during a catch and run that went for a 10-yard touchdown last Sunday.

According to Pro Football Focus, Lewis has forced a league-leading 29 missed tackles in just 59 touches.

Lewis, with a little help from one of the greatest coaches in the history of the game, has defeated defenders in many ways.

Patriots coach Bill Belichick said on his WEEI radio show this week:

One of the most impressive things about Dion is how versatile he's been. He's caught balls out of the backfield. He's caught running back-type routes on linebackers, but he's also caught some receiver-type routes from being extended—gos, double moves, slants, things like that. It's not all slip-screens or hitches or that type of thing. They are actually receiver-type routes. In the running game, he has shown he can run inside. He has shown he can run outside. He has shown he can run with power…put his shoulder down and push the pile for a couple yards. And then he has shown he is very elusive in space with his quickness and change of direction. Sometimes [defenders] don't even hit him. He has good balance and good strength to break tackles, and the quickness to avoid them.

Cowboys defensive coordinator Rod Marinelli believes Lewis will be a special NFL player.

"They use him very well," Marinelli said. "They get the ball to him in different ways. Some of the ways they run the ball allow him to use his vision. He gets upfield so quickly. He sees it really well. He's kind of like a [Darren] Sproles with more of an inside dimension. He's physical, and his change of direction is something else. He's pretty unique in that way."

The mystery of Dion Lewis? It's not where he came from anymore. It's how to contain him.

Dan Pompei covers the NFL for Bleacher Report.