Chiefs have an X-factor that's not Patrick Mahomes or Travis Kelce

It's finally here. The start of the NFL regular season is upon us. The Kansas City Chiefs kick off their season at home during "Monday Night Football" against the Denver Broncos on Sept. 14. This franchise is obviously one of the most popular in the NFL, and a Monday night game against a longtime rival is the perfect way to kick off their season.

Heading into the new season, quarterback Patrick Mahomes is back after suffering an ACL and LCL injury. Travis Kelce is also back for what may be his final season in the NFL. But, the Chiefs have an X-factor on their coaching staff that may be overlooked amid the big names.

Chiefs' defensive coordinator Steve Spagnuolo could be their secret to success

In a Wednesday feature, Jeff Howe of The Athletic gives inside intel on each NFL team as the new season starts. For the Chiefs, he really emphasizes that the team's longtime defensive coordinator, Steve Spagnuolo, is their secret to success.

Spagnuolo has been with the team since 2019. Regardless, Howe highlights his work as being what could really make the Chiefs' comeback this season.

"Defensive coordinator Steve Spagnuolo's reputation is well-established, and he's still maddeningly frustrating to compete against," he notes in the piece. "Coaches around the league rave about Spagnuolo's ability to enter a game with a plan and then build counterattacks from there."

He adds that the coordinator "knows how offenses will adjust to his looks, so he'll evolve throughout the game, and that's even more of a challenge in the fourth quarter when the Chiefs are playing with a lead."

It helps that the Chiefs boosted their defense in the draft. They took cornerback Mansoor Delane as a first-round pick, and he's expected to take on a big role out of the gate. They also snagged defensive tackle Peter Woods in the first round. So, consider these new players who could shape the next era of this team.