Will the Celtics' defense improve next season?

Blame Avery Bradley for setting the bar pretty high.  At his camp a few weeks ago, he said:

"Everyone keeps telling me that Marcus is a great defender and ... I'm excited about that," said Bradley. "Because Rondo is a great defender as well. Last year, he still played great defense, but this year I feel like he's going to take it to an even different level. I feel like we have a chance to be a top-10 defensive team in the NBA this year."

It all depends on how you define "top-10," but the Celtics may not have to far to go to reaching that goal.  Admittedly, that "ranking" as the 13th best defensive team from last year is a little misleading.  In Hollinger's defensive efficiency ratings (that factors in pace and points scored per 100 possessions), the Celtics ranked a more realistic 20th in the NBA.  They're 19th in defensive rebounding rate and ranked near the bottom of the league in generating steals and blocks.  According to NBA.com/stats, they were third to last in allowing field goals made at the rim and fourth to last in FG% at the rim.  So how does a team that finishes so poorly in several defensive stats boast a better defense than more than half the league?

We know that Stevens is known as an analytics guy, so here are some more numbers to crunch.  At the beginning of last season, Tom Ziller introduced the idea of the Green Triangle, a measure of how a team ranked in the three most efficient areas of the floor: in the restricted area, corner threes, and free throws.  Ziller meant for the Green Triangle to represent offensive effectiveness, but turn it on its head and it's also a great measure for how well your team defending those high efficiency shots.

As previously, the Celtics ranked poorly in defending the restricted area.  The Celtics averaged only 4.2 blocks per game (8th worst in the NBA), playing most of the season without a true center after Vitor Faverani was lost to a knee injury and Joel Anthony seldom played after getting traded to Boston.  Opposing teams attacked the Celtics at the rim the 6th most times and finished 59.8% of the time.

How did Ainge address that issue?  Tyler Zeller.  It wasn't the sexiest off-season move, but as Kevin suggests, he may not exactly be the answer, but could be a serviceable stop gap:

When guards are constantly allowing dribble penetration there is really only so much a big man can do, which was a major problem for the Cavaliers. With strong perimeter defenders like Avery Bradley, Marcus Smart, Rajon Rondo and Jeff Green, Zeller could have a career year defending the paint.

Zeller has displayed intelligence when it comes to positioning, rotations, and in help situations, despite being surrounded by open-the-floodgates defenders in Cleveland. This is crucially important when it comes to playing true team defense, which is why his presence should automatically help Boston this season.

The Celtics were just above the league average in allowing free throws (and for what it's worth, the world champion Spurs were dead last in getting to the line so maybe free throws aren't all they're cracked up to be).  A lot of that can be attributed to the lack of a rim protector and teams forcing the issue at the rim, but according to ESPN Boston's Charge Watch, the Celtics drew a total of 129 charges last season with Gerald Wallace tallying 24, Jared Sullinger 19, Jeff Green 16, Kelly Olynyk 15, and Avery Bradley and Rajon Rondo 10.  To put that into some perspective, the last Doc Rivers team drew only 83.  Although they struggled at the rim and to some extent allowing teams to get to the line, Boston was 16th in the league in forcing their opponent to shoot a mid-range, long-2 and more importantly, 6th in the league at forcing teams out of the corner 3.  That translates to a lot of defensive rotations and close outs.

After Kevin Garnett was traded and Doc left, a lot of the defensive DNA went with them.  KG had always been the defensive quarterback calling out coverages and audibles at the line.  Last season, Stevens utilized what he had and that was a roster flush with athletic wings (not unlike his gritty teams at Butler).  Jeff Green has always been a plus defender on the perimeter and Courtney Lee was a Celtic for over two months last year.  And keep in mind that a bulk of those games were without Avery Bradley and Rajon Rondo who played a total of only 324 minutes together in 15 games.

Most of these stats are completely anecdotal, silver linings in a forgotten season that some fans wouldn't even see the point of looking for silver linings. Cynics will say that the numbers are so on the fringe that they're not worth counting, but it's a start and it does show Stevens' ability to get his team to work. We can talk schemes and the value of analytics, but in the end, defense is all about attitude. When Bradley made the bold prediction that the team could make the playoffs, he put his faith in his teammates ability and desire to be a good defensive team.  The rebuild might end up being longer than anticipated, but at least the foundation is solid.