When Kyle Shanahan took over as coach of the San Francisco 49ers in 2017, one of his first targets for defensive coordinator was Vic Fangio, only to be turned down when he made the request to the Chicago Bears.

When Shanahan was preparing for DeMeco Ryans to leave for a head coaching job after the 2022 season, he once again hoped to get Fangio as a replacement only to miss out when Fangio signed with Miami before the job became open.

When the defensive coordinator job opened again the next year, Fangio opted to stay closer to home and take the same job with the Philadelphia Eagles.

Now instead of having Fangio on his side, Shanahan will have to figure out how to beat his defense when the 49ers (12-5) visit the Eagles (11-6) in a wild-card game on Sunday.

"I've tried all the times that there's been an opportunity," Shanahan said Wednesday. "He's always been with someone else when that's happened. I mean, I tried really hard in '17 when we first came here and I tried like two other times on separate occasions. So, Vic's a guy that I've always respected, gone against a number of times before I became a head coach, so that's why I respect him so much and through the process been able to become friends with him."

The matchup between Shanahan's offense and Fangio's defense will be one of the most intriguing of wild-card weekend as the two have been among the most influential coaches in the NFL.

Several teams throughout the league have searched for disciples of the Shanahan scheme to run their offenses, while several are running versions of a defense that Fangio has perfected.

The Shanahan offense has evolved from the one Kyle's father, Mike, used to win back-to-back Super Bowls with the Broncos in the 1997-98 seasons, relying heavily on the outside running game with a heavy use of motion and play-action.

That offense has helped the 49ers make it to two Super Bowls and two more NFC title games since 2019, with quarterback Brock Purdy and running back Christian McCaffrey helping it excel this season.

"Everything's packaged well together and he's a good play caller during the game," Fangio said. "You always know that, and everything they do has a purpose and a reason."

Fangio has been one of the top defensive minds in the NFL since returning to the pros as Jim Harbaugh's defensive coordinator in 2011. He relies heavily on schemes with two deep safeties and thrives by disguising coverages and limiting explosive plays.

Fangio helped the Eagles win the Super Bowl last year in his first season with Philadelphia and has them in position for another possible playoff run.

"Vic schematically, he has always been the best to me," Shanahan said. "As good as anyone there is. Has a very sound scheme that he doesn't need to change up very much. It just naturally changes with how he does his coverages, how he does his fronts, the personnel groupings he does. He's very good at getting a beat on what you're trying to do and making you adjust."

The respect is mutual and the two coaches have formed a good relationship over the years.

That led to Fangio being a frequent visitor at 49ers practices in the 2022 season, the year after he had been fired as head coach in Denver.

"I thought there was a chance that the d-coordinator that we had could possibly get a head coach job the next year, so I wanted to be prepared," Shanahan said. "So, Vic and I were talking about that stuff a lot and hoping that could possibly work out if we did change or get a new coordinator."

That happened when Ryans got hired as head coach in Houston after the Niners season ended with a loss in the NFC title game to the Eagles. But it was too late for a Fangio-Shanahan pairing.

"I remember the morning of our game versus Philly, I think it was, he signed with Miami so lost him that day," Shanahan said.