DALLAS — There has been little mystery with Alabama’s offense this season. The Crimson Tide have a 6-foot-3, 242-pound Heisman Trophy winner at tailback in Derrick Henry and the plan has been to swing that sledge hammer as many times as it takes to break the defense.

Michigan State is the next wall in the way.

The third-ranked Spartans face No. 2 Alabama on New Year’s Eve in a College Football Playoff semifinal at the Cotton Bowl, and they are determined not to crack.

“As the game progresses, people wear down,” Michigan State co-defensive coordinator Harlon Barnett said Sunday. “You get tired of hitting that big back. Boom. Again. Here he comes again. Boom. Again and again and again. And so you have to have the mental toughness to be able to say, ‘Hold on. We’re going to hold up and we’re going to keep smacking him. Keep hitting him.’

“It’s a test of wills and his will has won out a lot of times this season.”

Michigan State linebackers Riley Bullough and Jon Reschke tweeted at Henry the night he won the Heisman how much they were looking forward to the challenge.

“Can’t wait Derrick!!” was Reschke’s post to @KingHenry_2.

Henry set Southeastern Conference records this season with 1,986 yards rushing, 521 coming in the fourth quarter.

The old football saying for a running back such as Henry is that he gets stronger as the game progresses, but Tide quarterback Jake Coker has a little different perspective.

“He stays the same and everybody else changes,” Coker said.

So how does Michigan State plan to hammer Henry?

Replicating a 240-pound tailback in practice is nearly impossible. Michigan State (12-1) has used freshmen linebackers Kenny Willekes (6-3, 223) and T.J. Harrell (6-1, 209) on the scout team as ball carriers to give its defense the feel of tackling a big target.

It’s not necessarily a matter of scheme. Alabama (12-1) has faced plenty of loaded boxes, with defenses crowding seven and eight players near the line of scrimmage.

“We understand what we’re facing and that he’s a fall-forward back,” Barnett said. “He’s not getting knocked back too many times.”

And when Henry gets into space, those long arms help keep defenders at bay.

“He’s definitely a stiff-arm runner,” Michigan State co-defensive coordinator Mike Tressel said. “With a guy that big you talk about taking out his legs, but sometimes he doesn’t let you get in there.”

Michigan State ranks ninth in the country in rushing yards allowed per game at 113.1 and 22nd in yards per carry at 3.55. The Spartans’ front seven is talented but not huge, with 275-pound nose tackle Malik McDowell and no starting linebackers listed above 230 pounds. The Spartans keep it simple defensively, play sound fundamentals and commit plenty of bodies to stopping the run.

“Well, we’re just going to keep bullets flying,” Tressel said. “That’s the way we play defense. We fill with just about all 11 people on a run play.”