Chip Kelly was one of NFL's least aggressive head coaches in 2014

It's no secret that Eagles coach Chip Kelly has a reputation for being aggressive. During his time with the Oregon Ducks, he earned the infamous "Big Balls Chip" nickname. His aggressive tendencies carried over into the NFL, too. According to Football Outsiders, Kelly was the second most aggressive coach in 2013 when it came to going for it on fourth down.

But then something changed. In 2014, Kelly was actually one of the league's least aggressive coaches. According to FO, the Eagles head coach ranked 25th out of 33 head coaches in their "Aggressiveness Index" stat. His overall score was a 0.65, which is less than the league average of 1.0. The only coaches who were less aggressive include: Bruce Arians, Doug Marrone, Mike McCoy, Jeff Fisher, Mike Smith, and Dennis Allen. Three of those men are no longer head coaches in the NFL.

On fourth down plays from the 31-37 yard line, Kelly went for the first down zero out of four times. On 4th-and-2 plays, Kelly decided to go for it one time out of seven opportunities. On 4th-and-1 plays, Kelly had this team go for the first down three times out of nine. Overall, Kelly's Eagles only went for a first down four times out of 104 fourth down opportunities.

In Kelly's defense, FO writes that their metric may have unfairly punished him at times.

"You may also be surprised to see the allegedly super-aggressive Chip Kelly down near the bottom of the list. In his first season, Kelly was one of the league's more aggressive coaches. He went on 12 of 110 qualifying fourth-down opportunities, where an average head coach would have gone on 8.2, which gave him an AI of 1.46. That was second in the league to Rob Chudzinski. (We did not run an article on the site with those AI numbers from 2013, but they appeared in Football Outsiders Almanac 2014.)

At first glance, it looks like that aggression disappeared in 2014. Then I looked a bit closer, and Kelly's 2014 AI rating actually exposes some problems that we need to fix in the Aggressiveness Index formula going forward. The AI formula controls for teams being naturally aggressive when they fall behind, but it doesn't yet control for teams being naturally conservative with big late leads. As a result, we end up "punishing" Kelly for two third-quarter punts against Carolina in Week 10, both of which came on fourth-and-2 near midfield. They also came with the Eagles winning 31-7 and then 38-7, so it's hard to fault the decision. We also discovered that the AI formula doesn't adjust for tie scores late in the fourth quarter. So in Week 8 against the Cardinals, the "expected" odds that Kelly would go for it on fourth-and-1 from the 2 don't adjust for the fact that the score was tied with two minutes remaining and even the most aggressive coaches are going to send in the kicker to get a lead. Of course, that's not necessarily the best move... the Cardinals had two minutes to score a field goal to tie or a touchdown to win, and a 75-yard Carson Palmer touchdown pass to John Brown gave them a victory. (You can relive that play in the Week 8 Clutch Encounters article.)

We hope to work soon on some further improvements to Aggressiveness Index which will adjust for these sorts of situations, as well as an expanded AI metric that will measure other aggressive moves such as when coaches go for 2 and when they settle for conservative long field goals instead of aggressive touchdowns in late-game situations where a field goal ties or wins the game."

So why was Kelly less aggressive? Perhaps the plethora of injuries to the team's offensive line played a factor. Perhaps Kelly didn't fully trust LeSean McCoy in short yardage situations. Nick Foles and Mark Sanchez were struggling and weren't always the most reliable players either.

Moving forward, Eagles fans should hope to see the Kelly who was more aggressive like he was in 2013. Perhaps the addition of Kelly's preferred one-cut runners such as DeMarco Murray and Ryan Mathews will encourage him to go for it more often. Increased aggressiveness may or may not lead to more wins, but for a guy with Kelly's nickname it did feel he was a little too conservative last season. Anecdotally, at least.

Kelly has arguably been the most aggressive coach this offseason when it's come to player acquisition (and departure). Perhaps his aggressiveness off the field will translate to more aggressiveness on it this season.