Each week, Neil Greenberg will look at which AP top 25 teams teams are likely to be upset by a team that is either ranked lower or not ranked at all.

A team’s win probability is based on applying the model from Wayne Winston’s book “Mathletics” to my own point spread, which is derived from the Simple Rating System. Home-field advantage is worth 3.3 points and the standard deviation of point differential is 16.9 points.

No. 2 Florida State at Louisville. Chance of a Louisville upset: 49.8 percent. Vegas line: Florida State -3.5.

I’ve already laid out a case that Florida State has not yet proven enough to be part of the college football playoff picture, and this week may prove my case even further.

According to Football Outsiders F/+ combined rankings, Louisville has the best defense in the country, one which is aggressive, disciplined and keeps the opposing passing game in check. Here is the quality of defenses faced by Florida State so far in terms of their F/+ combined rank:

Clemson was FSU’s toughest defensive challenge to date, but that was also a game in which Heisman Trophy-winning quarterback Jameis Winston was ineligible to play. However, a questionable overtime decision by Tigers Coach Dabo Swinney helped the Seminoles avoid the upset.

In the win against Notre Dame, the only other top-20 defense on the schedule so far, the Seminoles needed a second-half rally and a touchdown reversed in the final seconds to secure the victory.

Louisville will be a tougher task than both.

The Fremeau Efficiency Index, one of the components of Football Outsiders F/+ metric, calculates the Cardinals defense allows their opponent to earn just 24.3 percent of the total number of yards available based on starting field position, best in the nation. Florida State accumulates 47.2 percent of those yards on offense, 52nd highest among 128 teams.

Louisville ranks ninth in defending the pass per S&P+ defensive rating, a college football ratings system derived from both play-by-play and drive data. Florida State ranks 15th for passing on the offensive side of the ball. Plus, according to ESPN, opposing quarterbacks have an adjusted Total QBR of just 14.7 against Louisville — the best mark in the country.

It could be a tough night for Winston and the Seminoles. Expect an upset.