DENVER — DeForest Buckner started the job that Stephon Gilmore finished.

Buckner has been the catalyst for so many other plays, so many other players in his three seasons in Indianapolis.

If Shaquille Leonard is the beating heart of the Colts defense, Buckner is its spine, the critical center who makes everything possible for the rest of the limbs. When Buckner is at the top of his game the way he was Thursday night against the Broncos, the Colts are hard to beat.

Buckner tormented Denver’s offense all night.

The big defensive tackle racked up eight tackles, two sacks, a tackle-for-loss, a pass breakup and a forced fumble, making big plays in key situations from start to finish.

Buckner’s first sack nearly gave the Colts offense the sort of easy field position Indianapolis desperately needed. His second essentially shut down a Denver red-zone opportunity, pushing the Broncos into an unlikely third-and-goal that led to Grover Stewart’s blocked field goal. He made three tackles on Denver’s failed final drive in regulation.

On the play before Gilmore’s game-winning pass breakup, Buckner teamed with Bobby Okereke to stop Melvin Gordon a yard short of the sticks.

“How about that?” Colts head coach Frank Reich said. “Coming off that elbow? Sack, pressures, tackles. He’s a force, and I just feel like he’s really getting on with this injury, as he kind of gets used to that, he’ll continue to play great.”

Buckner is only playing with an arm and a half right now.

He is dealing with an elbow injury, the kind that forces him to wear a massive brace on his big left arm and nearly knocked him out of Sunday’s game against Tennessee. The pain in the elbow was so bad that Buckner didn’t decide he was playing against the Titans until an hour and 45 minutes before kickoff of the Titans game.

“It’s a significant injury, but thankfully, it’s one that you can find a way to play,” Reich said. “I think it’s painful at times, in certain movements.”

But in one sense, Buckner’s decision on whether to play against the Titans, and then in dominant form against the Broncos, is a decision he made long ago.

Buckner almost always answers the bell.

He has missed just two games in his career, only one due to an injury despite playing a position that has wreaked havoc on his body over the course of his time with the Colts. Buckner played with a dislocated MCP joint and a badly sprained ankle in his first season in Indianapolis, battled back and knee injuries a year ago, has already fought through a back injury at the beginning of training camp and a strained adductor in his hip that limited Buckner against the Jaguars.

“I love the game,” Buckner said. “If I can go, I’m going to be out there, I’m going to give everything I’ve got, because when I leave the game, I don’t want to have any regrets.”

He’s been hurt badly enough before that the Colts have had to place him on a pitch count a couple of times.

When that happens, the Indianapolis defense often suffers.

Buckner might not have Leonard’s maniacal energy, but he makes up for it by example, by showing up and playing no matter what is putting him in the trainer’s room that week.

“To have a guy like that fighting through all the injuries just to be out there with his family, that’s a big thing for us,” nose tackle Grover Stewart said. “He makes guys want to go.”

Buckner’s presence also opens opportunities for the rest of his teammates.

Without fail, Buckner is the player opposing offenses try to double-team the most, intent on preventing the two-time Pro Bowler from wrecking their entire offense.

“I don’t force anything, I’m just myself,” Buckner said. “I love building connections, personal connections. I just feel like that goes a long way, especially when you’re going through hard times.”

From the sounds of it, Buckner’s elbow is a hard time. He’s already been limited in two of five games due to injury, and the severity of the elbow injury makes it sound like he might not be back to full strength for a while, even though he played 81% of the snaps, his usual workload, just four days after barely being able to go against Tennessee.

One of Buckner’s biggest strengths is his length, and the elbow isn’t letting him use his reach the way he would like.

“A little bit hard to long-arm with it, stuff like that,” Buckner said. “But I’m glad they hooked me up with a good brace to give some security.”

Buckner is the security for the entire Colts defense.

It should come as no surprise that the team’s two best defensive performances of the season featured Buckner playing like a man possessed. When Buckner’s healthy and dominant, the rest of the Indianapolis defense often follows suit.