How the Boston Celtics became a top-10 defense

Two days before the 2014 NBA trade deadline, Boston Celtics coach Brad Stevens huddled his team at a Phoenix hotel and issued a challenge. The rookie head coach wanted his Celtics -- 17 games under .500 coming out of the All-Star break but ranked 14th in the league in defensive rating -- to clamp down over the final 28 games of the season and make a charge at being a top-10 defense.

Stevens didn't have visions of some crazy second-half surge, but he knew a top-10 defense would give Boston an honest-to-goodness chance at being competitive sometime in the future. Finishing the season strong would have set a confident tone heading into the summer.

It never happened, of course. The Celtics watched their captain, Rajon Rondo, elect to skip a trip to Sacramento a few days later in order to celebrate his birthday in Los Angeles, and Boston went 6-22 to close out the season while ranking 24th in defensive rating over that span.

Undaunted, Stevens again challenged his team the following offseason to make defense its backbone. But it wasn't until Boston dealt Rondo to the Dallas Mavericks in mid-December for a return package that included Jae Crowder that the Celtics really seemed to embrace the notion. It's not hard to connect the dots -- Boston dealt away a player that had let defense become an afterthought for one that now spearheads a defense that desires to force opponents into submission.

Stevens knows 10 games is far too small of a sample to get comfortable, but 21 months after challenging his team to embrace the idea of a defensive DNA and become a top-10 defense, his Celtics own the third-best defensive rating in the NBA early in the 2015-16 season. On the heels of back-to-back smotherings of Russell Westbrook's Oklahoma City Thunder and James Harden's Houston Rockets, the Celtics have a growing buzz around their defensive tenacity.

"We play hard," Crowder told reporters after Monday's win in Houston. "Guys don't like that in this league. Guys want an easy, flowing game. But we play hard, and a lot of guys don't like it."

How did Stevens build this top-10 defense? It's certainly not a coincidence that Boston's defensive identity changed after the Rondo swap. It paved the way for Marcus Smart, the No. 6 pick in the 2014 NBA draft, to eventually elevate to a starting role and brought aboard Crowder, who is now the team's starting small forward and the NBA leader in steals per game (3.0).

Crowder's former squad, which couldn't rid itself of Rondo fast enough this offseason, visits TD Garden on Wednesday night. Boston is still owed a first-round pick from that swap and stands to collect it this summer if it falls outside the top seven. It's another asset in Boston's overflowing wagon of draft picks that could be utilized to further thrust this team toward true contender status.

But until those chips are cashed in -- whether via the draft or by trading for established talent -- the Celtics seem content to lean on their new defensive identity to keep them competitive every night.

It starts with Smart, who certified himself as a defensive menace in his rookie season but clearly has All-Defense potential. The Celtics simply are not the same team without him, as evidenced during his three-game absence earlier this month when he suffered a sprained big toe.

Smart plays with fire and intensity and seems to make at least one highlight-caliber play each night. That might be launching a 3-pointer while falling into the crowd, but more likely it'll come on the defensive end. Like producing a one-handed steal and full-court outlet pass in one motion against the Rockets, or a chase-down block against the Thunder, or hurling his body on the floor to coral a loose ball against the Spurs.

Smart missed 10 of the 11 shots he took during Monday's game in Houston but still emerged plus-30 in plus/minus because of the way he helped Boston defend. Don't get it twisted: Smart infuriated Westbrook during Sunday's win in Oklahoma City, then helped Boston bottle up MVP-caliber Harden just 24 hours later (though Houston's overall disarray didn't hurt Boston's cause).

The Smart and Crowder combo currently pairs on Boston's first unit with the team's best defensive frontcourt of Amir Johnson (who added much-needed rim protection) and Jared Sullinger (who has been a rebounding machine during an impressive start to the season). That quartet has been able to mask any difficulties expected with Isaiah Thomas on the floor. Thomas is at a disadvantage with his size (5-foot-9) but is still a competitive defender, and the NBA's player tracking data suggests he is holding his assignments to 9.9 percent below their season field-goal percentage (opponents are shooting just 32.2 percent against him overall).

What's more, Boston experiences no drop-off when it goes to the bench. While working his way back from a calf injury, Avery Bradley has been utilized in a reserve role, giving Boston another defensive-minded guard to roll in. The Celtics' second unit typically features Evan Turner and Jonas Jerebko, two players added last season who give Boston willing and versatile defenders who are able to switch and prevent teams from attacking in the pick-and-roll.

And, through 10 games, it's third-year big man Kelly Olynyk who owns the best defensive rating on the team at 85.1 (Turner and Jerebko are not far behind). Synergy Sports defensive data grades Turner, Thomas and Olynyk among the league's elite defenders (all ranking in the 94th percentile or better based on points allowed per possession defended).

Boston’s secret weapon this season? The Celtics are generating steals at an impossible rate, with opponents turning the ball over on a staggering 19.4 percent of possessions. Stevens said Monday that it's simply his players putting themselves in the right positions and utilizing their natural instincts to create turnovers.

Boston’s halfcourt defense has been an absolute menace when able to set itself. As the Celtics struggle to generate consistent offense, Stevens knows this defense can't relent.

"It’s gotta be our DNA," Stevens said. "If it’s not our DNA, we’re in trouble."

On Monday night in Houston, Stevens challenged his team to limit Houston to 35 second-half points. Boston dominated the third quarter while holding Houston to 13 points on 5-of-17 shooting and outscored the host Rockets by 19 while racing away. The Celtics might have hit Stevens' desired second-half mark if not for Houston's late-game run against the end of Boston's bench.

The Celtics didn't have the desire nor the necessary talent to embrace Stevens' challenge 21 months ago in Phoenix. They do now. And it's this defense that may ultimately define just how successful Boston can be this season.