Boise State defensive tackle Mike Atkinson enters his senior season lighter than at any other time in his college career — 306 pounds.

That number tells more than just his weight.

It’s the result of a more mature, more dedicated, healthier player — one who has become a key leader on the Broncos’ rebuilt defense, and one who for the first time will be asked to serve as the centerpiece of the defensive line.

“This is by far the most excited I’ve been for a season,” said Atkinson, a 6-foot space-eater from Windsor, Ontario, who was as heavy as 332 pounds in 2009. “I’ve learned from the best players in the nation and they went on to the next level, so that’s what I really want to do this year — I want to try to take everything I have to work on my technique and my fundamentals and be the best I can be.”

Atkinson and junior tackle Ricky Tjong-A-Tjoe are the only returning linemen who played extensively last year. The top five linemen are gone — all to NFL training camps, including first-round draft pick Shea McClellin, third-round pick Tyrone Crawford and sixth-round pick Billy Winn.

Atkinson has recorded six tackles for loss, three pass breakups and one forced fumble in 25 career games as a backup to three-year starter Chase Baker. But those numbers don’t show his true value, which is in the run game.

“He takes up a lot of space and he’s very powerful,” senior middle linebacker Tommy Smith said. “I really love it for me. He’s taking up at least two blocks, sometimes three. When he does that, we’re always winning on defense.”

Atkinson has overcome heaps of adversity, much of it his own creation, to reach this point.

He was suspended for the first three games of his freshman season after he was charged with driving under the influence. He also dislocated an ankle that year, which limited his playing time.

He got off to a strong start as a sophomore but was suspended for the last nine games for an unspecified violation of team rules.

Coach Chris Petersen granted him a third chance last year — and Atkinson has thrived since. He expects to graduate in December.

“Knowing it was my last chance,” Atkinson said of how he was able to transform himself. “… I always keep that in the back of my mind. I’m always ready for any situation now.”

Said Petersen: “Mike has done a nice job the last couple years of doing what we need him to do. … When a guy crosses the line, all eyes are on him for a long time and sometimes it’s even harder because we’re paying even closer attention and there’s no leeway. But that also can be the beauty of this whole thing, to see a guy figure it out and do right.”

Atkinson’s off-the-field improvements have carried over onto the field.

He is more fit and agile than earlier in his career, which has kept that old ankle injury from bothering him as much. He can handle more consecutive plays now, which will be important in the starter’s role.

“Whether it’s school or football, he just goes about his business day to day,” said defensive coordinator Pete Kwiatkowski, who also coaches linemen. “… He’s quick and strong and he’s a hard guy to move. He’s real important to us in the run game.”

Atkinson, who didn’t start playing football until eighth grade, likely will play professionally after this season. He was the 20th pick of the CFL Draft last spring, going to Hamilton.

Atkinson didn’t even know the CFL Draft was taking place when he was selected.

“It was a good surprise,” he said, “knowing I have the opportunity to go to the next level, no matter what.”

His options likely would expand with an impact senior year.

So, too, would the Broncos’ prospects.

“Just be the anchor on the line,” Atkinson said of his goal. “Make sure no one gets through the middle, keep the pressure on and make everyone else’s job easier.”

Chadd Cripe: 377-6398, Twitter: @IDS_BroncoBeat

Projected depth chart, defensive line

Stud end

Beau Martin (6-2, 250, so.) OR Sam Ukwuachu (6-4, 222, fr.): Martin, a walk-on who transferred from Colorado State Pueblo, and Ukwuachu, who played some wide receiver in high school, have shown the potential to wreak havoc in camp. “They’re both playing their tail off,” defensive coordinator Pete Kwiatkowski said. “They’re both being physical. It comes down to who’s going to make plays, who’s going to produce, and they’re both doing that right now.”

Nose tackle

Mike Atkinson (6-0, 306, sr.): He lifted a team-best 575 pounds in the back squat in the spring.

Greg Grimes (6-0, 293, sr.): He has appeared in just 18 games in his career but needs to provide much-needed depth this year.

Tackle

Ricky Tjong-A-Tjoe (6-3, 296, jr.): He recorded 9.5 tackles for loss and 4.5 sacks in his first two seasons. He’s in great shape and could be a disruptive force in his first season as a starter.

Darren Koontz (6-3, 274, sr.): He has bounced between end and tackle and will fill the spot with the most need. Jeff Worthy (6-3, 285, fr.) also could play here.

End

Demarcus Lawrence (6-3, 242, so.): The transfer from Butler Community College in Kansas has lived up to his recruiting billing. “Demarcus is doing a great job, and has certainly taken steps since the spring,” coach Chris Petersen told BroncoSports.com on Friday. “His effort and focus are really good right now.”

Tyler Horn (6-5, 265, so.): He made seven tackles and 1.5 sacks last year as a true freshman and has played well in fall camp, competing with Lawrence for the starting job.