One of the universal practices surrounding the NFL every week is watching film.

Teams competing against each other in a given week view detailed opponents’ records from previous games and encounters. This typically begins at the beginning of the week for the coaches and the entire team and extends beyond more specific breakdowns into position group meetings.

For the 49ers (3-3), who are preparing this week to host the 5-0 Chiefs on Sunday, the film study has taken on a more emotional, if painful, tone.

The 49ers had no choice but to watch the tape of their last game against the Chiefs, eight months ago in Super Bowl LVIII, a crushing 25-22 overtime loss in Las Vegas.

“Everyone understands we lost the two Super Bowls to them,” 49ers head coach Kyle Shanahan told reporters this week. “That can cause a little bit of post-traumatic stress when you turn on the tape. That’s human nature. But you have to be careful not to get involved in it. This game has nothing to do with previous games, that was last year.”

This is the 10th time in NFL history that the previous Super Bowl has been rematched the following regular season, and the defending champions are 6-3 in those games.

And that’s not all: Since Shanahan took over in San Francisco in 2017, the 49ers are 0-4 against the Chiefs – and even have a double-digit lead in both Super Bowl defeats.

The 49ers were up 10-0 in the first quarter in February and held a lead in the fourth quarter and overtime, but were outrebounded by Chiefs superstar quarterback Patrick Mahomes.

Again. For the second time since the 2019 season.

“It’s definitely a little emotional,” 49ers defensive end Nick Bosa told reporters about watching the tape of last year’s Super Bowl loss. “But at this point it’s just one game, so we’re just watching the tape and trying to learn from it. Lots of similarities to last year. A few new guys but a really good defense and offense obviously have No. 15 (Mahomes) back there. So always dangerous.”

San Francisco linebacker Fred Warner tried to rationalize the severity of the duel by saying this duel was “probably not as dramatic as everyone else probably thinks.”

“(We’ve) moved on,” he said. “New season, new game, new teams, new players.”

While there haven’t been any major changes with the Chiefs, the 49ers are much different than the team that lost in February. In the offseason, they fired defensive coordinator Steve Wilks and replaced him with Nick Sorensen and hired former Chargers head coach Brandon Staley as assistant head coach to help with defense.

Injuries have also plagued the Niners this season. They are missing running back Christian McCaffrey (Achilles tendonitis), defensive tackle Javon Hargrave (torn triceps), linebacker Dre Greenlaw (torn Achilles tendon), safety Talanoa Hufanga (torn wrist ligament), offensive lineman Jon Feliciano (knee) and kicker Jake Moody (right ankle).

With the exception of Hufanga, all of these players started in the Super Bowl. Other former 49ers — defensive linemen Arik Armstead and Chase Young and safety Tashaun Gipson Jr. — signed with other teams in free agency.

One of the most important matches will take place in the trenches. Perhaps the most glaring reason the 49ers lost the Super Bowl was their failure to block Kansas City defensive tackle Chris Jones, who wreaked havoc in crucial moments of the game. San Francisco’s rookie right guard Dominick Puni will be primarily assigned to Jones on Sunday.

“He’s one of the best D-tackles, if not the best, in the league, so I’m excited about that,” Puni told reporters.

Be careful what you wish for.

The most visible key element of this game will be San Francisco’s two quarterbacks, Mahomes and Brock Purdy.

Purdy had a strong performance, throwing for 255 yards and three touchdowns with no turnovers last week in Seattle.

As if the aforementioned challenges weren’t enough for the 49ers, the Chiefs head into the game after their bye week, and do you know what that means? Kansas City head coach Andy Reid has a career record of 21-4 in the regular season following his team’s bye, the best of any head coach (at least 10 games) since the bye was implemented in 1990.

“You think about what’s in there, but as far as the way it plays out in the game, there’s really no connection, and you try to make sure that’s not the case,” Shanahan said.

As of Sunday’s kickoff, it will have been 252 days since Kansas City won its third championship in four years, its second at the expense of the 49ers.

“It’s not like we can take revenge for the loss in the Super Bowl,” the San Francisco left tackle said after the win in Seattle. “The ship has sailed.”