FOXBORO -- Joe Tiller knew he had something special in Rob Ninkovich when he first saw him on the football field.

The former Boilermakers head coach was overseeing the first spring workouts in 2004 after Ninkovich transferred from Joliet Junior College. He and the rest of the coaching staff were trying to decide whether to use Ninkovich as a tight end or defensive end, but that debate ended quickly.

“In his first spring practice, when we tried to block him as a defensive end, we couldn’t block him,” Tiller recalled with a laugh. “So we left him at defensive end.

“Rob was a good player because he had a toughness about his play -- a natural toughness that you just can’t coach. He was an aggressive guy, a tough, tough guy. You couldn’t hurt him,” Tiller added.

“It’s great to watch him now with New England, because the Patriots are getting the most out of his talents. He just keeps on ticking. He’s just a guy who shows up for work every day. Those are the kind of guys that are easy to coach.”

It’s taken a couple of years, but Ninkovich has managed to evolve into one of the most important defenders on the New England roster. A free-agent signee for the Patriots prior to the 2009 season, while working at both left and right defensive end and outside linebacker this season, he has 32 tackles (26 solo), four forced fumbles (best on the team), five sacks and six quarterback hits (both good for second on the team) in eight games.

The highlight of the 2012 season for Ninkovich was an overtime sack and forced fumble of New York quarterback Mark Sanchez, a sequence that caused Patriots coach Bill Belichick to call Ninkovich a “Jets killer” and that fueled suggestions that he could be one of the most underrated defenders in the NFL because of the combination of his versatility and pass-rushing production.

“He’s not a flamboyant player. He doesn’t draw much attention to himself, and he probably doesn’t get the recognition he truly deserves,” said Tiller, a lifelong Lions fan who said he has started rooting for the Patriots because of Ninkovich. “But he’s pretty darn valuable.”

Ninkovich had a slow start to the year, but he said the key to his most recent run of success is a decision to take a page of his college experience and start incorporating more of the high-energy approach he employed in college, which got him 16 sacks in two years at Purdue.

After a September win over the Bills where he finished with seven tackles, a sack and a forced fumble, Ninkovich pinpointed the reason behind his renaissance, and offered a mea culpa for his performance to that point in the season.

“I hold myself accountable for the previous couple of games, [and] I didn’t feel like I was active enough in just changing things up on the offense,” Ninkovich said after the win over Buffalo. “I was able to go out there and change up my rush styles and change up my inside-outside moves, what I was going to do previously coming into this game. Just get back to [being] more energetic and just getting after the ball. That was my mentality coming into this game.”

The decision to take a page out of his old approach was met with approval by some of his old coaches.

“I’m glad to hear him say that he was going to go back to his old style at Purdue,” said Tony Samuel, who coached the defensive ends while Ninkovich was at Purdue. “You put that style with the other techniques he’s acquired and developed over the years, there’s no question you’ll have yourself a great football player.”

For Ninkovich, it’s been a long journey to the NFL, one that started in earnest right after high school -- specifically, Joliet Junior College. Bob MacDougall, his coach at JJC, said that even as a teenager, Ninkovich showed the sort of nose for the ball and pass-rushing skills that have defined him the last couple of years in New England.

“He came out of high school as a fullback and a defensive end -- he was a little undersized, if I remember correctly,” MacDougall said of Ninkovich, who had 23 sacks in two seasons at JJC. “But he didn’t let that stop him. He was just an extra tough kid with a load of talent. He practiced hard, and was part of a great group of kids. Just a great athlete with good speed and great strength. He always seemed to be around the play.

“I remember talking to a coach at Purdue, and he asked me if I thought he could play in the Big Ten. I said, ‘If you give this kid a chance, he’s going to start for you sometime before his fourth game at Purdue.’ As a defensive end, he had good strength and great closing speed. But he also had the intangibles you look for in a player. It was clear he had that special thing you look for. It’s corny, but he has the heart of a champion.”

After two seasons at JJC, he transferred to Purdue, where it was quickly evident he was going to flourish. Samuel, who worked with him at Purdue and is now the head coach at Southeast Missouri, said he was a coaches’ dream.

“He brought a great work ethic, plus he always had this bright look in his eye -- this kid wanted to play so bad,” Samuel said of Ninkovich. “He had every single tool I could think of -- he had a high motor, great hands, great quickness. Anything I told him, I could just see him working it in his mind over and over. He’d come back again, and he’d just get it. You wouldn’t have to tell him twice. Just a great guy -- a coaches’ dream. Quiet, humble and blue collar. He made it easy on me.”

But even after a collegiate career where he was second-team All-Big Ten as a senior in 2005, it took him a few years to find his footing in the NFL. A fifth-round pick of the Saints in 2006, he was dismissed by New Orleans and later the Dolphins. (He was inactive for 12 games in 2007 for a Miami team that went 1-15.) After a second stint with the Saints, Sean Payton told him the only way he was going to make it in the league was by working as a long snapper before letting him go.

Ultimately, he was waived four times by New Orleans and Miami before landing in New England, signing a free-agent deal with the Patriots prior to the start of the 2009 season. But he didn’t click with New England, at least not right off the bat: He didn’t start a game for the Patriots until the 2010 season, and it wasn't until the end of that year that he became a key part of the Patriots defense. That set the stage for an impressive 2011 campaign, where he was only one of two NFL defenders to finish the year with at least six sacks and two picks. (Baltimore’s Terrell Suggs was the other.)

“He was a tremendous defensive end in college, but he also was clearly a hybrid guy who can rush the passer and drop into coverage,” Samuel said. “He had the speed moves, he had the ability to drop the shoulder -- he could dip under bigger tackles. He had great quickness and a great ‘get-off’ motor, even as a college player, and you just knew that was going to translate nicely somewhere in the pros.”

Over the last year-plus, the 6-foot-2, 260-pound Ninkovich posted impressive numbers, all while working as both left and right defensive end, as well as outside linebacker. But instead of slapping a label on him, Patriots coach Bill Belichick has referred to Ninkovich as an “end of the line” player on several occasions, while his teammates have hailed his versatility.

“Rob’s been playing that position since he’s been here: end of the line, standing up, three-point stance, whatever it is, it’s been pretty much the same. I wouldn’t say there’s been a lot of change in what he’s done -- some, but not a lot,” the coach said. “But, he’s certainly been productive and that’s good to see because he’s had a lot of production really all season, but (especially) the last four or five games.”

“In a Bill Belichick defense, you never know what position you’re going to be in, so it’s good to know multiple positions,” said defensive tackle Vince Wilfork. “Ninkovich is one of those guys who we’ve moved around a lot. He’s done a very good job of doing his role. On any given Sunday, Bill may say, ‘Hey, we want you to play here,’ so you’ve got to be ready.”

Now, for the first time in his career, Ninkovich has some professional security: The 28-year-old signed a two-year extension worth $4 million last September, and has clearly claimed a spot as a part of New England’s defensive foundation. Pro Football Focus has him graded at +10.4 for the year overall, the fourth-best figure on the roster, and he's on pace to hit double digits in sacks for the first time in his career.

Not bad for the son of an Illinois ironworker who had to start in junior college.

“I always get questions about who my favorite players were as a coach,” said Tiller, who was the head coach at Purdue from 1997 until 2008 and also worked with former Patriots Matt Light and Rosevelt Colvin. “I’m always reluctant to say, because I had a lot of favorites, guys who always did what was asked of them and were great team guys. Rob would certainly fit in that group. I still love watching him play. When I watch my old players, I’m almost like a parent because I watch them more than I watch the game, and that’s the case with Rob.”