What the Vegas odds say about the KC Chiefs-Steelers playoff game. (It’s historic)

In 1990, as the NFL sought to capitalize on growing TV revenue, it announced an expansion of its playoff format. The new Wild Card Round would include four games, two in each conference.

That’s 31 years ago, and not one team in that timeframe has been as large of a betting favorite as the Chiefs are Sunday.

The Chiefs are favored 12 1/2 points against the visiting Steelers at Arrowhead Stadium, the largest line in Wild Card Round history, per information available on Stathead.

The previous largest of 11 points occurred three times — the Packers against the Vikings in 2012; the Steelers against the Dolphins in 2016 and the Saints against the Bears last year.

All three favorites won.

All three covered the 11 points, too.

In other words, anything other than a Chiefs victory Sunday would be historic — because no one else has even been placed in this position.

Here’s why it’s happening now: The Chiefs beat the Steelers 36-10 just three weeks ago, and that final score was actually closer than the game indicated. The Chiefs led 30-0 and removed their starters for nearly the entire fourth quarter. The Steelers do not rate particularly well in any of the major offensive or defensive metrics, while the Chiefs won nine of their final 10 games. It all points in one direction, and the Vegas oddsmakers are on board.

The Chiefs finished 8-9 against the spread in the regular season after failing to cover the line against the Broncos last week. The Steelers had the same mark.

The over/under for the game is 46 points — the exact number these two teams hit in Week 16.

In other games this weekend, the Bengals are favored 5 1/2 points against the Raiders; the Bills are favored by 4 1/2 against the Patriots; the Buccaneers are favored 8 1/2 points against the Eagles; the Cowboys are favored by 3 versus the 49ers; and the Rams are 4-point favorites facing the Cardinals.

Despite not having the first-round bye in the AFC, a luxury the Titans earned instead, the Chiefs opened the postseason as the favorites to win the AFC Championship and advance to a third straight Super Bowl. They are listed at 2-to-1. The Titans and Bills are tied for second at 7-to-2.

The Chiefs are 5-to-1 to win the Super Bowl, which trails the Packers, who are 7-to-2. The Packers earned the only bye in the NFC as the conference’s top seed.

PITTSBURGH STEELERS (9-7-1) AT KANSAS CITY CHIEFS (12-5)

When: 7:15 p.m. Central, Sunday

Where: Arrowhead Stadium

Betting line: 12 1/2 points

Over/under: 46 points

Steelers against the spread this season: 8-9

Chiefs against the spread this season: 8-9