Five teams on the decline in 2015

Jason Bridge/USA TODAY Sports

Twelve teams in the NFL make the playoffs every season, and we know that about half of them won't return the following year. The trick is guessing who'll be in and who'll be out. But don't worry, Football Outsiders has a complicated projection system to figure out the answer -- or at least what the probabilities are. Because given how much random chance is involved in an NFL season, every team goes into the year with at least a 1-in-400 shot at winning the Super Bowl.

Below, I'll look at the five teams that are likely to decline compared to last season, according to our forecast. The projection system predicts each team's DVOA (defense-adjusted value over average, explained here) on offense, defense and special teams using a number of variables, including performance during the past three years, coaching experience and personnel changes. Then we simulate the season a million times to get a wide range of possibilities that account for every team's best-case and worst-case scenario.

Click here for a look at five teams likely to improve in 2015.

(Note: We overhauled out projection systems this summer, so the forecasts below might be different from what you've seen from us earlier this offseason)

Arizona Cardinals (11-5 in 2014)

Mean Wins: 6.7 | Playoff Odds: 18.4% (26th) | Wins Super Bowl: 0.8% (25th)

By far our strongest candidate to decline in 2015, Arizona had absurdly good fortune last season, finishing 11-5. That might sound like a ridiculous statement about a team that lost its starting quarterback for much of the season, but the Cardinals won a lot of close games in which they got the right breaks. Teams that outscore opponents by 11 points all season should go roughly 8-8, not 11-5. Based on play-by-play breakdown, Football Outsiders' metrics ranked Arizona as the 22nd-best team in the league last season.

The return of Carson Palmer should improve the offense, but not by much. Palmer really didn't play much better than Drew Stanton last season. (Ryan Lindley is another story; he was horrendous.) Standard stats just make Palmer look better than Stanton because he faced such an easy slate of defenses. When he was hurt, Palmer avoided Seattle (twice), San Francisco (twice), Detroit and Denver. The defense, meanwhile, will probably be good but not as good as it had been in 2012 and 2013 because there's a new coordinator and a lot of departed talent (primarily Larry Foote and Antonio Cromartie).