The Kansas City Chiefs (4-0) won another close game in Week 4, defeating the Los Angeles Chargers (2-2) on Sunday, 17-10.

The two-time defending Super Bowl champions are now the last remaining unbeaten AFC squad and one of just three undefeated NFL teams along with the Minnesota Vikings (4-0) and the Seattle Seahawks (3-0).

Each of Kansas City’s four victories to begin the season have been by one possession, which doesn’t bode well for its chances at a three-peat, based on NFL history.

Led by head coach Mike Ditka, quarterback Jim Harbaugh, Pro Bowl running back Neal Anderson and a top 10 defense, the Chicago Bears started the 1991 season 4-0 and 9-2 before settling for an NFC wild-card berth at 11-5. They lost to the Dallas Cowboys, 17-13, in the wild-card round.

Head coach Marv Levy’s Buffalo Bills started the 1988 campaign 4-0 and eventually 11-2 prior to limping into the playoffs at 12-4. The Bills defeated the Houston Oilers in the wild-card round before falling to the Cincinnati Bengals in the AFC Championship Game.

After opening the 1993 campaign 4-0, the Philadelphia Eagles lost six in a row and eight out of nine. Their season-ending three-game winning streak wasn’t enough to get them into the playoffs.

In the final year pre-Bill Belichick and Tom Brady, the 1999 New England Patriots started 4-0 and 6-2 but lost six of their final eight contests and missed the postseason.

Unlike any of its four predecessors, Kansas City is not only the defending Super Bowl champion, but also a back-to-back title winner. In addition to history being stacked against them, however, the Chiefs have other concerns, primarily the loads of injuries on offense.

Just in the first month of the season, Kansas City has lost three key contributors to significant ailments that are expected to keep the players out long-term.

Offseason acquisition Marquise “Hollywood” Brown went down with a shoulder injury in the preseason that is likely to keep him out for the year. Fellow wideout Rashee Rice suffered an injury during Sunday’s win against the Chargers, and the fear is a season-ending torn ACL. Starting running back Isiah Pacheco fractured his fibula in Week 2 and was placed on injured reserve in mid-September.

If there’s any team able to sustain these huge losses, though, it’s the Chiefs.

The group still has one of the best head coaching/quarterback/pass-catcher combos in NFL history in Andy Reid, Patrick Mahomes and Travis Kelce, respectively. Kansas City should continue to have success in close games, too, thanks to having one of the most clutch kickers in the sport in Harrison Butker, as well a mastermind on the sidelines in defensive coordinator Steve Spagnuolo.

The Chiefs also have a good chance of hosting at least one playoff game by virtue of winning the AFC West. They’ve won eight division titles in a row (including the last six with Mahomes under center) and are already two games ahead of the Chargers (2-2), Denver Broncos (2-2) and Las Vegas Raiders (2-2) through the first month of the season.

Even with the trio of crushing injuries on offense and history saying their Super Bowl aspirations are in trouble, it’s never a smart bet to count out the Chiefs.