By Rob Mahoney
March 12, 2013

Boston Celtics defenseKevin Garnett (left) and Avery Bradley have keyed the Celtics' defensive resurgence. (Noah Graham/NBAE via Getty Images)

By Rob Mahoney

The notion that the Celtics are better off without Rajon Rondo -- a notion inspired by Boston's seven straight wins following Rondo's season-ending injury -- has thankfully faded. So much of that faux-debate was predicated on rushed judgment and flawed assertions, as many trumped up the importance of an incredibly basic measure of performance (win-loss record) without much regard for the mitigating factors at work (wins during that streak came at the expense of  the Clippers without Chris Paul, good teams on the tail end of a back-to-back and some of the league's worst overall). A lightning-rod point guard was linked to a sexy, prepackaged narrative, and sometimes that's all it takes to bait us all into a silly conversation.

Don't get me wrong: the specific merits of Rondo's play are debatable, as are the kinds of lineups in which his talents are most constructive. But there was (and is) little tangible evidence to suggest that Boston is a better team without one of its best players.

What we've actually seen in Boston is a complete defensive resurgence that has little to do with the presence or absence of Rondo. At the time of Rondo's injury, I wondered aloud if the shifting burden of the Celtics' offense would wind up taking its toll on Kevin Garnett and Paul Pierce, in particular. Age is an undeniable factor when it comes to projecting the future performance of those two, and yet they remain so crucial to Boston's execution on both ends of the court. If a heavier offensive workload were to wear down Garnett to any tangible degree or prevent Pierce from checking an opponents' best wing players, then the Celtics' vaunted defense (and playoff chances) would surely suffer. Instead, we've seen the opposite. Although it has little to do with the redistribution of shot-creating responsibilities, Boston's overall defense has ranked as the second stingiest in the entire league since Rondo's exit.

Overall, the Celtics have held opponents to 4.4 fewer points per 100 possessions since Rondo exited the lineup -- a significant differential that is roughly equivalent to the gap between a top-10 defense and one in the bottom five. Considering that Boston was already one of the better defensive teams in the league to begin with, this huge boost has allowed the Celtics to win 14 of their last 19 games without really making any tangible improvements to their underwhelming offense. Further, with a defense this good, the Celtics have re-asserted themselves as postseason players. The Heat are still miles ahead and the Pacers have played out a more convincing (and sustained) season, but the East's flimsy second tier accommodates even those with such unbalanced success.

As with most defensive improvements, the Celtics aren't running anything radically different from before, save the selective implementation of a matchup zone defense that finally seems to be gaining some traction. Celtics head coach Doc Rivers explained that defensive option to Chris Forsberg of ESPN Boston:

“It’s really a matchup zone more than a college zone,” said Rivers. “We switch everything, but we guard the ball, whereas a college zone, they are standing there with their arms up -- you can’t do that in our league. Our guys actually go out and guard the ball. They play our man defense in pick-and-rolls; whenever the ball goes to the post, we draw up into a man; under 5 seconds we go up into a man. So it’s a lot of changes and you have to be really alert to do it. Kevin Eastman has been the guy, he’s done a terrific job.”

Rivers expects to keep going back to the zone and his players -- yes, even Kevin Garnett -- like it.

“Kevin wants to just play man-to-man and he thinks you should just guard your own guy, and if everybody did what he did, then it’d be perfect defense,” said Rivers. “But he’s gotten into it. He likes it [the zone], too, at times because of the switching."

That zone is a useful tool, but a situational one that doesn't come remotely close to explaining Boston's incredible defensive success. This is still a team that relies on familiar man-to-man principles to guide its every-play execution while using this kind of variant defense as a specific counter or a change of pace. Boston's zone notably helped clinch an improbable comeback win against the Pacers last week, but we shouldn't allow a good stretch in an important game to overstate the value of a systemic quirk that's more gadget than engine.

It makes more sense to attribute Boston's defensive improvement to Avery Bradley, who has picked up right where he left off last season. Bradley, who suffered a season-ending shoulder injury at the end of last season, stalls ball handlers, throws opponents out of rhythm while executing their set plays, trails well around screens and has a great understanding of which way he can funnel his man. All of that makes him a great individual defender, but an even more important asset when paired with the likes of Brandon Bass or Chris Wilcox.

Boston has struggled through much of the season whenever Kevin Garnett stepped off the floor, and suffered an added loss when Jared Sullinger -- the Celtics' second-most effective big this season -- went down for the year. His absence meant that Rivers had little choice but to rely heavily on Bass and/or Wilcox, defensive limitations be damned. Yet almost 20 games into Boston's revival, Bass and Wilcox both are filling vital minutes and defending far better than expected. They each deserve credit for the positive trend in their performance, but Bradley makes the job of both players easier by gambling less often than Rondo and allowing fewer dribble-penetrators to attack the basket. Bass and Wilcox have been better, but it's Bradley's perimeter defense that reduces the number of times that either big has to rotate to help. When Bass or Wilcox are forced to help and protect the rim on play after play (as was the case with Boston's second unit earlier this season), then the team's overall defensive performance will inevitably suffer. But when a player like Bradley can stop a ball handler in his tracks and wall off the paint, then the number of situations in which Bass and Wilcox can be exploited shrinks significantly:

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Defensive rating (DefRtg) represents the points allowed by the Celtics per 100 possessions -- the lower the better.

Bradley may not be seen as a transformational defender, but the trickle-down effects of adding a staunch perimeter stopper makes things far more comfortable for the rest of the Celtics' lineup. Jason Terry is saved from unfavorable matchups and Courtney Lee can be assigned to defensive marks more judiciously. The season-ending injuries to Rondo and Keyon Dooling are hedged by Bradley's increased workload. Any 1-2 or 1-3 pick-and-rolls that opponents run can be handled more effectively, as Bradley can hound opposing wing players off the dribble and fight for position if they attempt to post him up. Garnett can rest for certain stretches because Bradley makes it easier for Rivers to rely on his second-unit bigs.

These are all relatively minor factors, but the context and stakes aligned for Bradley to make a broad and profound defensive difference on Boston's entire rotation. He's hardly the sole reason for the Celtics' awakening, but he's as close to a single impetus for their defensive renaissance as you're likely to find.

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