The Celtics have become feared and revered around the league for their dogged defense. Last season they finished fourth in defensive efficiency rating while making headlines and turning heads by turning around several games in their dying minutes.

This season they look to be even better. With Al Horford and Jaylen Brown joining a line-up that includes, Avery Bradley, Jae Crowder and Marcus Smart, the Celtics look set to improve their already dominating defense.

CBS Sports has already predicted the Celtics as a ‘lock’ for having a top-five defensive rating this season. With consistency and some solid additions the Celtics are certainly well-positioned to have a top-tier defense but with a drive and desire to push even further could the Celtics become the best defensive team in the NBA?

“The difference between a good defensive team and a bad defensive team is as little as three possessions.” - Brad Stevens

Maintaining an elite defense is hard. Since 2011 the Spurs are the only team to have maintained a top 5 defensive rating for more than two consecutive seasons. Even the Golden State Warriors during their 73-win 2015-2016 campaign failed to maintain their top-tier defensive rating from their 2014-2015 championship season.

This Celtics’ squad has a lot of natural defensive ability, but they didn’t earn their hard-nosed reputation on raw talent, they fight and scrap for every possession. In Stevens’ system effort is everything and hustle can win basketball games.

Players like Crowder and Bradley already fit Stevens’ defense-first orientated system perfectly, while players like Isaiah Thomas and Kelly Olynyk have made substantial strides in their defensive awareness. An important factor in this has been communication on the court, something the Celtics showed they could do very well last season as they switched heavily all over the floor.

With additions to the team there’s likely to be some growing pains on defense, but Horford is definitely an upgrade in the frontcourt. Also players like Smart and Rozier are on positive development paths to improve their respective games. Beyond this some addition by subtraction should help the Celtics get off to a strong start with David Lee’s poor spacing and Jared Sullinger’s lacklustre efforts no longer a factor. Although Sully’s rebounding will be missed.

“Basketball is like a war in that offensive weapons are developed first, and it always takes a while for the defense to catch up.” – Red Auerbach

That piece of Auerbachian wisdom is as true today as it ever was. The Boston Celtics, as if ever-guided by Red’s words, have ‘caught up’ and possess a thoroughly modern defensive unit. Several players on the roster are noted for their abilities to play multiple positions and are regularly called upon to do so.

Boston also has a large number of strong perimeter guards, perfect for counteracting the modern NBA’s heavy usage of three-pointers. The Celtics are one of the few teams in the league who can ‘go small’ without giving up their defense. Versatile bigs like Horford and Johnson give the Celtics options in a ‘small ball’ frontcourt while their multiple guards and wings, who are essentially all strong on defense, provide perimeter pressure to chase opposing guards off the three-point line.

This carefully crafted defensive unit is capable of wreaking havoc on opposing teams by constructing traps and forcing bad shots. On the other end of the court the Celtics have several options to space the floor with Olynyk, Jerebko, Horford and even Amir Johnson capable of hitting the long ball.

“On offense, it’s possible to take a break, to stand around a bit, let other players take over. On defense, if you take a break, a good offensive team will burn you. On the other hand, when you and your teammates are all doing the job – and you’re all that good – the great reward is watching the other team slowly suffocate.” - Bill Russell

To say the Celtics hung their hat on defense last season makes it seems as if they rested on their laurels. Really they made defense their calling card.

They’ve earned their reputation as one of the NBA’s best defensive units by fighting for every possession and diving on every loose ball. Last season The Celtics stole their fair share of games with a number of last-minute wins that were predicated primarily by the Celtics never-say-die defensive attitude. This season the Celtics will have to put defense-first again if they want to maintain and improve their record.

Under Stevens, Boston have become one of the most defensively minded teams in the NBA, continuing the tradition of playing the style of in-your-face, defense-first, basketball that has helped to define the Celtics as a franchise. Having the best defense in the competition doesn’t necessarily make you the best team in the league. But if it’s true what they say and defense wins championships then the Boston Celtics are in a good position to push toward contention and might be well on their way to Banner 18.