In Steve Spagnuolo the Kansas City Chiefs trust. With good reason.

Like most football coaches, Steve Spagnuolo has lived a nomadic existence.

Five seasons at Connecticut. Two in Maine. One with the Frankfurt Galaxy. Two with the Baltimore Ravens. In 40-plus years as a coach, he’s worked for 15 different teams. The closest he’s come to permanence is when he’s worked with Andy Reid, spending eight years with the Philadelphia Eagles and the last five years with the Kansas City Chiefs.

Given what he’s done with the Chiefs, it’s a good bet the defensive coordinator has a place in Kansas City for as long as he likes.

"I still think 'Spags' should be up for assistant coach of the year," defensive tackle Chris Jones said after the Chiefs harassed Lamar Jackson, the NFL’s likely MVP, into one of his worst-ever performances in last weekend’s AFC championship.

"What he’s been able to do with this defense from last year to this year, how we were able to overcome a lot of humps, how we were able to force a lot of guys to grow," Jones added. "Last year, we gave up a lot of big plays. This year, L’Jarius Sneed had an All-Pro year, should have been All-Pro. (Trent McDuffie) had an All-Pro year. You could go down the list."

It’s understandable for Patrick Mahomes and the offense to command most of the attention on the Chiefs, who are verging on New England Patriots-like dynasty territory with their fourth Super Bowl appearance in five seasons. Mahomes is a generational quarterback, capable of making plays even the Madden creators can’t imagine. His connection with Travis Kelce is particularly potent, with the two bumping the likes of Jerry Rice, Tom Brady and Rob Gronkowski down a notch in the record books.

But the Chiefs aren’t playing the San Francisco 49ers in the Super Bowl next weekend without their defense.

While the offense was a work in progress for much of the season, the defense carried the load, finishing second in the NFL in both points and yards allowed. Despite facing both Jackson and Josh Allen, Kansas City is giving up less than 14 points a game in the playoffs. Jackson finished with his lowest completion rate of the season while Allen had to dink rather than dunk, finishing with his fewest yards gained per pass attempt of the year.

No wonder Kansas City players broke out "In Spags We Trust" T-shirts after beating Baltimore.

"We believe in him wholeheartedly; he believes in us and we believe in each other," said safety Justin Reid, who organized the T-shirts. "Nobody goes out there and tries to play hero ball. We just play the defense, play our responsibility with intensity and a little bit of violence, and good things happen."

Spagnuolo’s success as a defensive coordinator is not new. He is, after all, the same guy who designed the game plan the New York Giants used to humble Brady and the previously unbeaten Patriots in Super Bowl 42 to conclude the 2007 season. Brady was under constant pressure and sacked a season-high five times in that game, which he later called "one of my least favorite football memories."

But what Spagnuolo has done in Kansas City, this year in particular, might be his best work yet.

To say Spagnuolo inherited a defense that needed work is putting it nicely. The Chiefs ranked 24^th in the 32-team league in points allowed in 2018, and were second-to-last in yards allowed. Kansas City also was going through a generational change, with players like Allen Bailey, Justin Houston and Steven Nelson giving way to Frank Clark, Derrick Nnadi and Charvarius Ward − who will see his old team in the Super Bowl.

In the five years since Spagnuolo arrived in Kansas City, the Chiefs have been in the top 10 in fewest points allowed all but one year.

"That was important. We have a history together, so I knew what to expect and where he would go with things," Andy Reid said when asked of the impact hiring Spagnuolo in 2019 had. "What he did with (the younger players) I thought was great, of teaching. All of his guys did that, they did a great job of teaching. The kids were receptive to it, and you’re seeing the rewards of it now."

Spagnuolo’s strength is fitting his schemes to his players, rather than the other way around. He’s also one of the best at making adjustments, particularly in the second half. In the last eight games, the Chiefs have allowed seven points or less in the last 30 minutes.

In the three playoff games, it’s been a total of 10. That’s right. In the second half against Tua Tagovailoa and the Miami Dolphins; Allen and the Bills; and Jackson and the Ravens; Kansas City allowed a touchdown and a field goal.

"When the games get bigger, the challenges get higher, (Spagnuolo) performs even better," Mahomes said after the AFC championship.

Spagnuolo will have to against San Francisco, which ranked second in the NFL in yards this season and third in scoring. Christian McCaffrey is a colossal headache for the entire defense, but he’s far from the only problem. There’s also Deebo Samuel. And Brandon Aiyuk. And George Kittle. Shall I continue?

Even Brock Purdy, who has been dismissed by many as a game manager, showed last week against the Detroit Lions that he’s not to be taken lightly.

But if there’s anyone up for the challenge, it’s Spagnuolo.

"Is it one of the better defenses? Yeah, I’d say it’s one of the better defenses that I’ve been around," Reid said Monday.

In Spagnuolo the Chiefs trust. With good reason.

Follow USA TODAY Sports columnist Nancy Armour on social media @nrarmour.

This article originally appeared on USA TODAY: Steve Spagnuolo's defense plays big role in Kansas City Chiefs success