KANSAS CITY, Mo. -- Upon being hired as defensive coordinator of the Kansas City Chiefs, Steve Spagnuolo wasted no time in formulating his take on many of the players he will have next season. He was into the video moments after signing his contract last month.

There's that kind of urgency. The Chiefs' 2018 season ended with an AFC Championship Game loss to the New England Patriots because of a faulty defense, and Spagnuolo was hired to fix that part of the team quickly.

"This is a long process to figure out who and what we have, how it fits," Spagnuolo said. "In today's NFL calendar, when you have just the nine weeks of offseason and then into training camp -- and even training camp is short -- it takes a little time to figure it out. The one thing I've always said, especially about defensive football, is you don't really get a good assessment of your players until you can put pads on and watch them play real defensive football.

"It will be a step-by-step process, but we're certainly knee-deep into it."

Shortly after losing to the Patriots, the Chiefs took a wrecking ball to their defensive coaching staff. They fired coordinator Bob Sutton and hired Spagnuolo as a replacement. Spagnuolo is a veteran defensive coach who worked for Andy Reid for eight seasons with the Philadelphia Eagles and was a coordinator for two other NFL teams.

"Steve will be a great addition to our defense and the energy that he brings and so on," Reid said. "I love Bob Sutton. Bob and I talk, we're still friends. Sometimes that's this business. Sometimes change can be good for both sides."

Only Britt Reid remains among the Chiefs defensive position coaches from last season, and even he moved from the line to linebackers. All of the new position coaches have played for or worked with Spagnuolo.

Brendan Daly (defensive line) and Matt House (linebackers) were on Spagnuolo's staff when he was head coach of the St. Louis Rams. One defensive backs coach, David Merritt, was an assistant with Spagnuolo with the New York Giants. The other, Sam Madison, was a defensive back for Spagnuolo with the Giants. That familiarity is no coincidence.

"Many of these guys I have a history with, and that's really, really important, especially when you start out this process," Spagnuolo said. "You can't sit in here and talk football unless you speak the same language. Believe it or not, every team you go to has a little bit of a different language, but we're all on the same page. We're advanced that way."

The Chiefs won't take a wrecking ball to their defensive roster. They will make some changes but intend to improve with many of the same players. The list includes linemen Chris Jones, Derrick Nnadi and Breeland Speaks.

"It's a new look for our defense," Reid said. "The guys are going to have to learn new things, which also can be healthy too."

The Chiefs will shift their base defense from a 3-4 to a 4-3, which will necessitate a position change for at least some players among their linemen and linebackers. Justin Houston and Dee Ford, for instance, were linebackers in the 3-4 but will be asked to play defensive end this season, if they remain with the Chiefs.

"Chris is a type of guy that can play in any scheme, and having a premier pass-rusher is a good thing to have, so Chris can do anything," general manager Brett Veach said. "He can play all along the line. Certainly, Nnadi will have a role as such a good, stout run defender. Breeland, most people and even our organization too thought his natural fit was more of a 4-3 [defensive] end, but we liked his versatility back a year ago as potentially a 3-4 [outside linebacker], too. I certainly think that we have a bunch of versatility along the line there. Justin [Houston] and Dee [Ford] too, both of those guys can play in this scheme and do well. We like the pieces that are in place, and we're anxious to get this offseason started."

In free agency and the draft, the Chiefs will be looking for help at cornerback and safety. Some of the defensive backs who wound up playing a significant amount last season were acquired by the Chiefs right before the season in trades or free-agent signings.