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Kevin Garnett, Celtics Defense Uncharacteristically Having Trouble Defending Pick and Roll

A little less than one-fifth into the season, the Celtics are still trying to solve some problems in an area that typically is their biggest strength.

Following Sunday’s overtime win over the Orlando Magic, the Celtics were two games above .500 but had allowed their opponents to score triple-digits in four straight games, and five out of the last six. Doc Rivers was blunt about his team’s defensive shortcomings weeks ago after a loss at home to the Philadelphia 76ers.

“Overall,” Rivers said, “we have not been a great defensive team so far this year,”

In the nine games since, the Celtics won six but have not gotten much better defensively. They are still giving up more than 100 points per game, allowing the fourth-highest opponent’s field goal percentage in the league and surrendering almost 104 points per 100 possessions — more than the lowly Raptors or Wizards.

The stock explanation for the dropoff from last season, when the Celtics boasted one of the league’s best defenses by every traditional and statistical measure, has been the difficulty of incorporating new players into the system. Jason Terry, Jared Sullinger, Leandro Barbosa, Courtney Lee and Jeff Green have all suffered defensive lapses — some more often than others — but the Celtics really have no more new players in their rotation than last season, when Brandon Bass, Avery Bradley, Mickael Pietrus and Greg Stiemsma played important minutes early on.

New faces alone do not explain why Boston’s pick-and-roll defense in particular has gone from outstanding to out to lunch. All of the flaws were on display in an especially rough loss to the Spurs, when Tiago Splitter seemingly spent the entire game taking uncontested layups and erupted for 23 points while hitting nine of his 11 shots.

When anybody other than Kevin Garnett and Rajon Rondo defended the pick and roll, the Celtics defense was a sieve. One clear issue was the guards’ failure to impede the pick-man’s roll to the hoop while recovering quickly enough to the ballhandler. Rivers has opted to switch on ball-screens more often this season, but that has only created more mismatches for the opposing team to exploit. Switching can be extremely effective as a quick fix — as it was against the Miami Heat in the conference finals — but Rivers surely wants to correct the pick-and-roll deficiencies without using switches as a crutch all season long.

The other obvious problem has nothing to do with the two players directly defending the pick and roll. Whereas Bass and Ryan Hollins had reputations as poor off-ball defenders when they came to Boston, they improved quickly alongside Garnett and got by on length and mobility in the meantime. Sullinger and Green have been slower to catch on, and neither player terrifies opponents as an athlete. Meanwhile, Terry has gotten caught ball-watching far too often, most infamously on opening night when he let Ray Allen glide past him into the corner for an opener 3-pointer.

In fact, poor coverage on the weak side and on the perimeter might hurt the Celtics even more than breakdowns in the paint, where a mistake means a free layup. At least a layup is only worth two points. When the weak side falters, the defense loses its shape and opponents suddenly get tons of open looks from beyond the arc. When those looks come from the corners, it is death for an NBA defense. The Celtics have allowed opponents to shoot close to 42 percent on corner threes this season, up from less than 31 percent last season. They were the best team in the NBA at defending all 3-pointers last year. This year, they are the seventh-worst — and it has everything to do with their shortcomings against the pick and roll.

“You look at San Antonio, I think every three they had came off pick and roll,” Rivers said. “I think they had one transition three where [Gary] Neal pushed the ball and pulled up and took a three, but [otherwise] every single one of their threes came off of our pick-and-roll coverage. And we have to be better.”

If the Celtics are to right their defense, this week would be the time. They host Deron Williams and the Nets on Wednesday, and if LaMarcus Aldridge‘s back is healed by Friday, he and rookie point guard Damian Lillard could run a clinic on how to execute the pick and pop. Then the Celtics travel to Milwaukee, where Brandon Jennings will try to slice up the C’s with pick and rolls as he did earlier this season, when he had 13 assists in a 99-88 Bucks victory.

The pick and roll is the go-to play for the vast majority of NBA teams, and for the past five years the Celtics’ ability to shut it down has set them apart from the competition. Now the Celtics are getting a look at how difficult life is when that strong point suddenly becomes weak.

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