Bill C’s annual preview series of every FBS team in college football continues. Catch up here!

Air Force Falcons Head coach: Calhoun (82-60, 12th year) 2017 record and S&P+ ranking: 5-7 (100th) Projected 2018 record and S&P+ ranking: 4-8 (112th) Five key points: Air Force is known for its rushing offense, but the Falcons’ fate has been tied mostly to defense. And the defense was really bad last year. Calhoun’s new defensive coordinator — whoever that may be — will deal with a far more experienced defense than last year’s. We’ll see how much of a difference that makes. QB Arion Worthman is awesome, but Air Force needs to figure out how to get more skill guys involved; defenses hit Worthman a lot last season. The secondary was green and banged up last year. That means lots of experienced pieces this time, plus some higher-upside sophomores. The schedule is not kind. Air Force might be favored in only two to four games, meaning the Falcons will need an upset or two to avoid their first multi-year bowl drought since 2003-06.

When Troy Calhoun took over for Fisher DeBerry as Air Force head coach, Paul Johnson was still at Navy, Stan Brock had just taken over for Bobby Ross at Army, and Air Force was nearly five years removed from a bowl bid.

Calhoun enters his 12th year having averaged 7.5 wins per year, but while he won between six and nine games in each of his first six seasons, the last five have been awfully volatile. The Falcons’ win total has changed by at least two games, one way or the other, each season, and they have won 10 games twice and lost 10 games once.

The driving force: defense. It comes and goes in Colorado Springs. Under coordinator Tim DeRuyter — who has since served as Texas A&M’s DC, Fresno State’s head coach, and Cal’s DC — the Falcons surged to 25th in Def. S&P+ in 2009, covering for an offense that was far worse than normal and dragging Air Force to eight wins.

Following DeRuyter’s departure, AFA’s Def. S&P+ ranking slipped for four straight years, bottoming out at 122nd in 2013. That was the 10-loss season, one that put Calhoun on the hot seat.

He responded with a second defensive surge. With Steve Russ at coordinator, the Falcons got aggressive, stuffed the run, lopped nearly 16 points per game off of their scoring defense, and improved to 61st in Def. S&P+. They went from 10 losses to 10 wins.

They’ve regressed in each of the three years since. Surge, regression, surge, regression.

Air Force was 118th in Def. S&P+ last season. They scored at least 38 points and lost in back-to-back weeks early in the season. The aggressive formula fell out of whack — the Falcons weren’t making enough plays to account for the big plays they were allowing, especially against the run.

Just two years removed from a surprising MWC title bid, they fell from 10-3 to 5-7, and only a 3-2 record in one-possession games kept the total from plummeting further.

In January, Russ left to take a position coach job with the Carolina Panthers. Air Force has not yet announced his replacement. Former Ohio head coach and Wake Forest and Indiana coordinator Brian Knorr has come aboard in some capacity, but it’s unclear what capacity.

Whoever is calling the shots, one thing is certain: the defense will dictate the rebound. The offense should be as steady as ever, but against a schedule that features five opponents projected in the S&P+ top 80, a one-dimensional team will struggle.

Offense

In 2016, quarterback Arion Worthman took over for an injured Nate Romine and thrived. Air Force averaged 39 points per game and finished on a six-game winning streak. His first loss behind center didn’t come until an early-2017 trip to Michigan. It was followed by quite a few more losses, though.

Defense was the root of AFA’s early four-game losing streak, as the Falcons allowed 40.3 points per game during the streak. But Worthman wore down, and with good reason: he was taking a lot of hits.

Check out the distribution of carries from the last two years:

2016 : 40 percent fullbacks, 31 percent tailbacks, 29 percent quarterbacks

: 40 percent fullbacks, 31 percent tailbacks, 29 percent quarterbacks 2017: 38 percent quarterbacks, 33 percent tailbacks/slot receivers, 29 percent fullbacks

Not including sacks, QBs went from rushing 208 times in 2016 to 270 times in 2017. The Air Force option offense is driven by reads, and through some combination of Worthman reading “keep it” and opposing defenses dictating that Worthman read “keep it,” Worthman kept it.

He rushed 205 times for 935 yards — his per-carry average sank from 5.8 in 2016 to 4.6, and his opportunity rate (carries generating at least five yards) fell from 46 percent to 39. He didn’t move backward often, but opponents appeared content with giving him three or four yards, getting a nice hit, and keeping the big-play guys from getting the ball.

Air Force was as efficient as ever but didn’t produce nearly enough explosive plays.

Worthman missed the last two games with a knee injury, and backup Isaiah Sanders engineered a 38-35 win over Utah State by rushing 43 times himself.

Worthman and Sanders are both back, and sophomores Donald Hammond and Beau English looked pretty good this spring. That’s good because if the QB continues to take this many shots, Air Force will need a lot of QBs.

Worthman’s still good, though. Air Force was still efficient, and he had his moments in the passing game. After going a woeful 2-for-12 combined against Michigan and San Diego State, he completed 52 percent of his passes at 19.6 yards per completion the rest of the year.

Granted, this is still an offense that doesn’t want to pass — Air Force was 1-4 when he threw more than eight passes in a game and 3-2 when he didn’t — but he’s got big-play guys. All three players targeted at least 20 times last year are back. That includes slot man Ronald Cleveland, who combined 11 catches with 44 rushes to gain a combined 679 yards. He’s electric and probably needs more touches. He averaged 5.8 touches in wins and just 3.7 in losses.

Cleveland might get more touches simply because someone has to. Top tailback Tim McVey and No. 2 fullback Jacob Stafford are gone, leaving fullback Taven Birdow as the only returning running back who rushed more than 45 times last year. Fullback Parker Wilson and tailback Nolan Eriksen now move up the depth chart, but after them? It’s unclear. Sophomore Kade Remsberg — by my count, one of only four former three-star recruits likely to see the field this year, along with Birdow, outside linebacker Lakota Wills, and perhaps sophomore cornerback Tre’ Bugg — could end up taking on a pretty heavy load if he’s ready.

There’s turnover on the line, but ... well, there’s always turnover on the line at Air Force. The Falcons had to replace four guys with starting experience last year and must replace five this year.

The key for isn’t year-to-year continuity, but game-to-game continuity. The Falcons had neither last year — eight linemen started at least once, and only two started all 12 games — and became a little bit leakier. They fell from second to 13th in stuff rate (run stops at or behind the line), and their always-bad Adj. Sack Rate ranking fell from 117th to 127th.

Sign up for the newsletter The Read Option A daily-ish mini-column on the college football thing of the day, with some other stuff too. Email (required) By signing up, you agree to our Privacy Notice and European users agree to the data transfer policy. Subscribe

Defense

The combination of success rate and IsoPPP is designed to ask two questions: how frequently are you successful, and how successful are you? For the Air Force offense, the answers were “quite!” and “not at all,” respectively. For opposing offenses, it was “sometimes” and “quite!” Air Force’s defense ranked dead last in FBS in IsoPPP, meaning the magnitude of the successful plays the Falcons allowed was higher than anyone else’s.

Here’s that in chart form:

Goodness. The Falcons gave up 3.2 gains per game of 30-plus yards (122nd) and 2.5 rushes per game of 20-plus yards (126th). You could gash them, and they couldn’t gash you, which put far too much pressure on the Air Force offense to stay on schedule and produce at the end of long drives.

This was perhaps to be expected considering that, while Air Force is always playing more upperclassmen and dealing with more turnover than the normal program, 2016-to-2017 turnover had to be italicized: six of the top seven linemen, four of five linebackers, and six of seven defensive backs had to be replaced. Add in a few injuries up front and a lot of them in the back, and you had a recipe for disaster.

You don’t tend to have massive turnover two years in a row, though. And while three key disruption pieces are gone — inside linebackers Jack Flor and Grant Ross and corner Marquis Griffin combined to make 36 percent of Air Force’s havoc plays last year — the Falcons do return about seven starters. That’s six more than last year.

The most proven are at outside linebacker. Kyle Floyd was Air Force’s version of a nickel back last year, and Lakota Wills recorded six tackles for loss (second on the team) as the rarest of Air Force commodities: a freshman contributor. He could be a massive disruptive force.

These two should have a solid line in front of them. Five of last year’s top six return, including another Academy rarity: a 320-pound nose guard (Mosese Fifita).

That leaves the secondary. Air Force tried as hard as it could to disrupt passing games, and while it sometimes worked (the Falcons allowed just a 56 percent completion rate and ranked 54th in passing success rate), when it didn’t, it was catastrophic. Opponents averaged over 15 yards per completion, and AFA matched its No. 130 ranking in rushing IsoPPP with a No. 130 ranking in passing IsoPPP. As attrition had set in, this unit was awful, allowing a 65 percent completion rate and 181.5 passer rating in the last three games.

Last year’s top five safeties return — including Garrett Kaupplila, who managed to finish as the fourth-leading tackler in the secondary despite missing the last nine games of the season with injury — and returning corners Jeremy Fejedelem, Robert Bullard, and Zane Lewis could get a push from a trio of sophomores (Tre’ Bugg, Elisha Palm, Gabe Otley).

Special Teams

Air Force has had one of the most consistently solid units in the country. In four years of Special Teams S&P+ data, the Falcons have been in the top 50 each year. That run could get tested by the loss of kicker Luke Strebel and all-or-nothing return man McVey. The Falcons still have punter Charlie Scott, and perhaps Ronald Cleveland could add “awesome kick returner” to his list of skills, but Strebel was excellent, making eight of 11 FGs of 40-plus yards over the last two years.

2018 outlook

Air Force has made only five hires in the last 60 years, and they were all pretty good.

Ben Martin led the Falcons to a top-six AP finish in just their second year of top-division football in 1958, then got them to the Sugar Bowl in 1970.

Bill Parcells stayed only one year before leaving to become the New York Giants’ defensive coordinator, and he went just 3-8, but he was Bill Parcells. We’ll say that was a pretty astute hire.

Ken Hatfield took over a team that had won just 13 games in five years and won the Hall of Fame Classic in his fourth season and engineered a top-15 finish in his sixth.

DeBerry took over in 1984 and damn near won a share of the national title in 1985.

Over 11 years, Calhoun has nearly as many 10-win seasons (two) and bowl wins (four) as DeBerry did in 23 (four and six, respectively).

Calhoun’s name is constantly associated with other job openings — a sign that either he’s got an active agent, he thinks he’s done what he can in Colorado Springs, or both — but he’s got another reclamation job this year. He’s got an exciting, if thin, set of offensive personnel, but his near-term fate might be decided by his defensive coordinator.

With a top-50 offense and a mere top-100 defense, Air Force should be able to return to the postseason. But S&P+ does not give the D the benefit of the doubt (nor should it) and projects the Falcons just 112th overall. That makes them a favorite in just two to three games and gives them a likely win total around four.

Maybe the future’s fine beyond 2018, but the last time the Falcons had back-to-back losing seasons, they were making a coaching change pretty quickly thereafter.

Team preview stats

All power conference preview data to date.