A Historic Line Movement
When Bo Nix fractured his ankle on the second-to-last play of Denver’s overtime victory against Buffalo, the betting market reacted swiftly. The Broncos went from 1.5-point favorites on lookahead lines to 5.5-point underdogs in a matter of hours. That 7-point swing represents one of the most dramatic injury-related line movements in playoff history.
If the line holds, Denver will enter Sunday’s AFC Championship as the biggest home underdog in Conference Championship history. The previous record holders: the 1977 Broncos at +4 against the Raiders, and the 1976 Raiders at +4 against the Steelers. Nearly 50 years of NFL playoff betting, and no home team has been this disrespected in a conference title game.
The question worth asking: Has the market overreacted?
The Math Behind the Movement
Before the 2025 season, Yahoo Sports surveyed 12 oddsmakers to estimate the point-spread difference between each team’s starting quarterback and their backup. The average differential they assigned between Nix and Jarrett Stidham? Just 3.85 points.
The actual line movement after Nix’s injury: 6.5 to 7 points.
That gap suggests the market may have overshot. Stidham isn’t an unknown commodity. He’s a seven-year veteran who started two games for Denver in 2023 after Russell Wilson was benched, completing 60.6% of his passes with two touchdowns against one interception. His 7.5 yards per attempt in that stretch exceeded Nix’s season average.
More relevant for contrarian bettors: the Broncos’ Super Bowl odds collapsed from +325 to +900 at BetMGM. That shift reflects public perception more than analytical assessment. When public money floods one direction, opportunity often exists on the other side.
Why Stidham Is Different From Most Backups
Stidham will become just the second quarterback in NFL history to make his first start of the season in a conference championship game. Roger Staubach did it in 1972, losing 26-3 to Washington. But Staubach was a Super Bowl MVP coming off an injury. He wasn’t an afterthought.
Stidham hasn’t thrown a pass in a regular season or playoff game since January 7, 2024. He took exactly four offensive snaps all year. The unprecedented nature of his situation is what’s driving the line. But unprecedented doesn’t mean hopeless.
Consider this context: Frank Reich is the only quarterback to win multiple playoff games after not starting in the regular season. He did it with Buffalo in 1992, engineering the biggest comeback in playoff history against Houston before winning again the following week. Nick Foles took over for an injured Carson Wentz late in 2017 and won a Super Bowl. Jeff Hostetler replaced Phil Simms in December 1990 and led the Giants to a championship. Backups can win when surrounding circumstances align.
Denver’s Real Advantage
The Broncos finished the regular season with one of the NFL’s best defenses. They allowed the fewest sacks in football, tied with the Rams at just 23. That offensive line protection will help Stidham, who was sacked five times in one of his 2023 starts. Sean Payton has had a full week to tailor the game plan to his backup’s strengths.
Denver also has home-field advantage at altitude. The thin air at Empower Field at Mile High affects visiting teams, and the Broncos went 9-1 at home this season. Stidham won’t be asked to carry the team. He’ll be asked to manage the game while the defense does the heavy lifting.
There’s a narrative element worth noting: Stidham was drafted by the Patriots in 2019. He spent three seasons in New England before bouncing to Las Vegas and eventually Denver. Playing against the team that let him go provides built-in motivation. These storylines don’t move betting lines, but they can affect performance.
The Contrarian Case
Public perception has already baked in the worst-case scenario for Stidham. The line reflects a team losing its MVP-caliber quarterback days before the biggest game of the season. What it may not fully account for:
First, the Broncos’ defense held Josh Allen to five turnovers in the divisional round. That unit doesn’t change without Nix. Second, Payton coached Drew Brees for years and has extensive experience maximizing limited quarterback play – he won games with Teddy Bridgewater and Taysom Hill in New Orleans. Third, the Patriots’ defense, while improved, ranks 23rd in DVOA. They benefited from four C.J. Stroud interceptions last week against Houston.
Home teams in conference championship games hold a strong historical record. Since 1970, they’ve won roughly two-thirds of these matchups. Denver being an underdog of this magnitude at home represents a significant deviation from historical norms.
What the Spread Is Pricing
At Patriots -5.5, the implied probability suggests New England wins roughly 70% of the time. Drake Maye has been outstanding this season, leading the league in completion percentage at 72% while throwing 31 touchdowns against just eight interceptions. The Patriots are 8-0 on the road.
But Maye has never played in Denver. He’s never dealt with the altitude or the crowd noise. And while his supporting cast is solid, New England’s path to this point came through games where opponent mistakes mattered more than New England dominance. The win over Houston featured five Texans turnovers. That’s not a sustainable formula.
The Broncos don’t need Stidham to be great. They need him to be competent – to avoid turnovers, move the chains occasionally, and let Denver’s defense control the game. His 2023 outings suggest that floor exists.
The Historical Parallel
The 2015 Broncos entered their AFC Championship against the Patriots as home underdogs. Different circumstances, of course – Peyton Manning was the starter, though he was a diminished version of himself after a midseason injury. That Denver team rode its defense to a 20-18 victory over Tom Brady and went on to win Super Bowl 50.
This Broncos team has a similar identity: elite defense, serviceable offense, home-field advantage. The parallel isn’t perfect, but it’s worth acknowledging. Denver has won in this building with quarterback uncertainty before.
Where Value Might Exist
At +5.5, the Broncos are getting more points than any home team in conference championship history. If you believe the market has overreacted to Nix’s injury by even a point or two, there’s mathematical value in taking Denver to cover. The moneyline at +200 implies about a 33% win probability. Given the defensive matchup and home-field advantage, that number may be too low.
None of this guarantees a Broncos cover. Stidham could struggle badly. The Patriots could dominate. But contrarian betting isn’t about certainty – it’s about identifying spots where the market may have overcorrected. A 6.5-point line swing based on expert estimates of a 3.85-point difference suggests overcorrection has occurred.
The Broncos embraced the “overdog” label all season after being underestimated. Now, as the biggest home underdog in conference championship history, they have one more chance to prove the doubters wrong.