Where is the Boston College Defense falling short this year?

One thing that is beginning to worry BC fans is that the defense doesn’t look as dominating as it did last season. The eye test alone tells you that there is just a different feel from last year’s defense to this year’s defense. This really shouldn’t be a surprise because the defense was just so good last season and there was only one way for it to go this year. Still, the blowout losses against Clemson and Virginia Tech raise concern and there is some curiosity to dive into the stats and see how far the defense is behind from last season’s group. Aside from the eye test what do the stats tell us about what is going on this season? A look at the most basic defensive stats statistics shows that the defense is well behind pace from last season in points per game, but not in many other areas:

Points Per Game Overall (2015,2016)

15.3/23.7

Points Per Game ACC Play (2015,2016)

18.4/40.7

Total Defense Yards Per Game (2015,2016)

254/253

Total Defense Yards Per Game ACC Play (2015, 2016)

293/407

Rushing Defense (2015,2016)

83/103

Passing Defense (2015,2016)

171/149

Opponent Third Down Conversion (2015,2016)

24%/30%

The points per game definitely jumps off of the page in both overall and ACC play only. Obviously the total yards have gone way up in ACC play but have remained identical in overall play. So how is the defense allowing so many more points per game, particularly in ACC play?

One explanation could be explosive plays allowed, which is categorized by plays allowed of 20+ yards or more. This stat tells us just how the unit has done preventing long passing plays this season. In 8 ACC games last season the unit allowed 22 explosive passing plays compared to 11 through three games this year. The difference is almost 1 more explosive passing play per game. We can take that stat a step further and see that the team has allowed a whopping 6 passing plays of 30+ yards this year in ACC play (2^nd highest in the league) compared to 11 last season.

The first reaction to these statistics is that the secondary players are not performing as well as the unit did last year, which probably is true. However, the pass rushers can’t be taken off of the hook here either. In 2015 the Eagles averaged 2.88 sacks per game in ACC play which is down to 1.33 this year.

The coaching staff might tell us that three games is too small of a sample size to be looking at statistics, especially considering Clemson was one of those three games. However, I would counter that the game against Georgia Tech who is 2^nd in the ACC in rushing attempts counters Clemson’s explosive offense. It’s clear that BC is more prone to allowing the big play this season, and time will tell whether the explanation is the secondary, the front seven, or both.