Cardinals vs. Broncos (-2.5): NFL Betting History of the 2.5-Point Spread

Shortly after the Denver Broncos covered the spread in a Week 14 loss to the Kansas City Chiefs – for their first ATS winning streak since mid-2021 – they opened as a 2.5-point home underdog in NFL odds against the Arizona Cardinals in Week 15.

Two days later, the Broncos flipped to a 2.5-point favorite after Kyler Murray suffered a season-ending injury in the Cardinals’ loss to the New England Patriots on Monday Night Football.

Same spread, different favorite for Sunday afternoon in Denver.

How Common Is a 2.5-Point Spread?

Since 2003, approximately 7.3% of all regular-season spreads closed at 2.5. It’s the fourth-most common number, behind only 3 (17.6%), 3.5 (10.8%), and 1 (10.2%).

Of those 330 regular-season games with a closing spread of 2.5, how many ended with a final margin of exactly three points?

Forty-four (13.3%), or about one in every seven or eight games. 

It’s the most common outcome in 2.5-point games – and the most common outcome in all games in NFL history.

Of course, the Broncos don’t have to beat the Cardinals by exactly three points to cover the spread. They can win by four points or 10 points, the second- and third-most-common outcome in 2.5-point spread games, respectively. Or they can win by nine points, 16 points, or 29 points to cover the spread.

But the number is 2.5, therefore some bettors see 2.5 and think, “field goal.” And historically, when a bettor sides with the 2.5-point favorite, they often lose.

In those 330 games from 2003 through Week 14 of the 2022 season, the favorite is 154-176 (.467) for an ROI of -10.7%. They’ve finished with a negative ROI in 14 of the 19 seasons, including seven straight entering 2022, though they are on pace to snap that streak this year (16-11, +12.8%).

Within the trend, there aren’t notable splits for home or away teams, bad or good teams, divisional vs. non-divisional games, etc. There are slight leans in some areas like, for example, underdogs in games with low totals (under 40) but not overwhelming.

Cardinals vs. Broncos Prediction

In his first 10 NFL seasons, Colt McCoy was horrendous against the spread: 8-19-1. In his last three seasons, he’s 4-3. That’s still not great, but it’s better than covering in 29% of starts over a decade.

If McCoy faces Russell Wilson on Sunday, I like the Broncos to cover and snap a five-game losing streak. If he faces Brett Rypien on Sunday, I also like the Broncos to cover and snap a five-game losing streak. 

Broncos 20, Cardinals 10