The Rams decided in January 2020 not to renew defensive coordinator Wade Phillips' contract, letting the veteran coach go after three seasons. They replaced Phillips with Brandon Staley, a 37-year-old Vic Fangio disciple who'd made an impression on Rams head coach Sean McVay with a Bears defense that held the eventual NFC champions to six points during a Sunday night victory the previous season.

That same month, McVay also hired an offensive coordinator. Wes Phillips, the Rams tight ends coach and Wade's son, introduced McVay to Kevin O'Connell, the 34-year-old former Washington offensive coordinator who'd made an impression on Phillips during their time together on Jay Gruden's staff.

Two months into O'Connell's and Staley's tenures in Los Angeles, the COVID-19 pandemic shuttered NFL office buildings and sent the two coaches home with their young children: three boys for Staley and his wife, Amy, and two boys and a girl at the time for O'Connell and his wife, Leah.

The two families spent the year together in a COVID bubble, home-schooling their kids in makeshift classrooms while O'Connell and Staley navigated a surreal offseason with no players in team buildings and no preseason games. The resurgent Rams rode the league's top-ranked defense to the NFC divisional playoffs; Staley moved across town a year later to become the Chargers head coach and was blocked from bringing O'Connell with him as his offensive coordinator. O'Connell won a Super Bowl with the Rams the next season.

Their families spent just a year together, but after that one season, O'Connell and Staley each left regarding the other as one of his best friends.

On Sunday, they will coach against each other for the first time in their friendship, both at the head of teams that made the playoffs a year ago and started 0-2 this season. Staley's Chargers have given up late scores in a pair of close losses; O'Connell's Vikings have lost six fumbles this year. The matchup has an urgency for both teams that alters the friendship between their coaches, if only temporarily.

"Brandon is a really close friend of mine, so I do know how competitive he is, and he knows the same thing about me," O'Connell said. "I don't know how much talking we will do with each other this week, but I care about him tremendously. I think he's a great, great football coach and is somebody who I respect as much as anybody in this league."

Staley also brings a defense that should look familiar to the Vikings. It's here where the friendship between the two coaches adds another twist to the matchup.

O'Connell made Ed Donatell, Fangio's defensive coordinator and Staley's former boss in Denver, his first defensive coordinator in Minnesota. O'Connell hired Donatell in 2022 to install a version of the scheme that Staley helped popularize with the Rams.

As O'Connell recalled this summer, he had former Dolphins coach Brian Flores on his initial list of defensive coordinator candidates in 2022, but "there was a lot going on last year that may or may not have contributed to me being able to bring him on in Year 1. He was definitely on my list, right at the top, and it just didn't work out in Year 1."

The Vikings defense gave up the fifth-most points in the league a year ago, though, as O'Connell's calls for a more aggressive defense went largely unheeded. Donatell and the Rams-influenced scheme were out, and Flores was in with the approach he had crafted in New England and Miami, featuring more blitz packages and press coverage techniques.

"The success that I had in the previous defense in L.A. with Brandon Staley and Raheem Morris, I believed in and still believe in that system," O'Connell said this summer. "But I wanted to build a system that was just a little more in alignment with my overall football philosophy."

What the Vikings defense is doing now bears little resemblance to how it played a year ago. In 2022, the team had the league's ninth-lowest blitz rate at just 18.9%. It ranks atop the league in that category now, blitzing 49.3% of the time. The Vikings employ three-safety nickel and dime packages and change coverage shells on the fly. The shift from match coverages to pure zone schemes, safety Camryn Bynum said, has helped simplify things for young defenders the Vikings need to think fast and react swiftly.

"I've played a match defense my whole career, so it's fun being able to play in this because it's a lot less stress on your plate," Bynum said. "It's also a different type of game that you have to play."

For the Vikings to get their first victory and stay within a game of first place in the NFC North, they will count on a defense that looks markedly different from how it did a year ago and their offense's ability to solve a scheme with similar roots to the one it faced in practice each day last year.

O'Connell and Staley will meet at midfield as friends after it's all over. One of them will head home with his team's season on a precipice; the other will head home with a badly needed win.

"I know how much of a challenge it's going to be for our team," O'Connell said. "I know how much of a challenge it's going to be coaching against them, and we've got to be at our best because he's bringing a good football team, a very well-coached football team, to U.S. Bank [Stadium] on Sunday."