By Going Small, the Celtics Have Discovered a Big Advantage Against the Bulls

When one team eliminates another in the NBA playoffs, the contributing factors go beyond just tactical adjustments and modified lineups. It's injuries, untimely slumps, convenient hot streaks, and great players expanding into supernovas.

The four-game erratic spasm between the Boston Celtics and Chicago Bulls has had a bit of everything. Rajon Rondo's broken thumb stands out as the series' pivotal moment—and it's clear the Bulls don't have a contingency plan for his absence—but let's remember that the 31-year-old guard made barely 40 percent of his shots this season. Rondo isn't Steph Curry, in other words, and the Celtics do deserve some credit for crawling out of an 0-2 hole thanks to the adjustments Brad Stevens made after that second loss last Tuesday.

Namely, Stevens' decision to start Gerald Green over Amir Johnson in Game 3 has proved to be a crucial point in this series. Hindsight makes it seem obvious now, but this was not an easy move. Johnson started 77 games in the regular season, and Boston's starting lineup averaged 113.7 points per 100 possessions this season, fourth highest among all five-man units that logged at least 250 minutes, per NBA.com.

But the playoffs are about matching up against one opponent, with their identifiable strengths and weaknesses. After six quarters of Chicago completely owning the offensive glass, Boston trotted out Tyler Zeller beside Al Horford after halftime of Game 2. The job was to stop Robin Lopez, and to beef up their own frontcourt.

But such an adjustment took the Celtics away from their identity. They were playing on Chicago's terms. So Stevens zagged by going small, which pushed Jae Crowder to power forward and made Horford the only big. That new starting lineup has been a wrecking ball in the 29 minutes they've played together this series, outscoring the Bulls by 25.4 points per 100 possessions.

Surrounding Isaiah Thomas—one of five or six best offensive players in the league, who just had one of the most impressive scoring seasons in NBA history—with shooters is Boston's identity, so Stevens correctly doubled down on what makes them great by spreading the floor and repeatedly calling for Horford to set a high ball screen 30 feet from the rim. This pick-and-roll has been Boston's best friend and Chicago's worst enemy.

With Johnson out of the game, Lopez is forced to guard Horford. This is a humongous dilemma for Chicago, and the primary reason his minutes went from 33 and 32 in Games 1 and 2, to 21 and 22 in Games 3 and 4, respectively. Lopez isn't quick enough to meet Thomas at the screen or switch onto the five-foot-nine dynamite stick.

One of two things happen when he tries: 1) Because he's just a smidge faster than Lopez, Thomas can either split the screen or turn the corner and get into the mouth of Chicago's defense, forcing help defenders to crash off the three-point line and deserting Boston's snipers. 2) In the event Lopez keeps Thomas at bay, Thomas can flip the ball to a rolling Horford, who suddenly has a four-on-three situation with zero rim protection as he barrels towards the hoop, or skip it directly to a shooter on the weak side whose defender is waiting for Horford in the paint.

The latter sequence is what sparked Green in Game 4, and the entire chain of events is why plodding big men can't survive in today's NBA. Green's insertion into the starting lineup is reminiscent of what the Golden State Warriors did in Game 4 of the 2015 NBA Finals, when they replaced Andrew Bogut with Andre Iguodala as a way to spread the court and make Timofey Mozgov obsolete.

Green does not impact the game like Iguodala, but just like those Cleveland Cavaliers two seasons ago, the Bulls have no counter. If Lopez doesn't come out of the paint, Thomas will repeatedly pull up for three-pointers and Chicago will lose by 30 points. If he does, all those terrible things listed above will occur. If Fred Hoiberg pulls Lopez, he's taking out one of his most important players in this matchup and reducing Chicago's primary advantage to rubble.

The small Celtics are better than the big Bulls. Stevens knows this, which is why Green for Johnson hasn't been the only change to his rotation. The first two Celtics off the bench in Games 3 and 4 were guards Marcus Smart and Terry Rozier (instead of Kelly Olynyk, Jaylen Brown, Johnson, or Jonas Jerebko). The Celtics wisely recognized that Chicago can't guard a small lineup and dominate the boards at the same time.

With three guards and five capable ball-handlers on the floor at all times, Boston puts pressure everywhere with a never-ending cycle of handoffs, screens, and cuts. Late in Game 3, the Bulls went point-guard-free against Rozier, Thomas, Smart, Crowder, and Horford—a dicey alternative Hoiberg may lean on for the rest of the series, given his rotten options. They were outscored by four points in four minutes, primarily because nobody could guard anybody.

On one play, with Dwyane Wade "checking" Thomas, Boston's best player drove right and forced Cristiano Felicio to slide down to cut off his momentum. Horford (Felicio's man) caught a pass at the elbow and was immediately met by a rotating Jimmy Butler, who didn't think twice about leaving Smart wide open on the opposite wing. Instead of standing still, catching Horford's swing pass, and probably missing a three, Smart sprinted into the paint and dragged Paul Zipser from the corner to prevent an open layup. Horford calmly read the defense, took one dribble past Butler, and threw a dart to the suddenly free Rozier, who nailed a three.

Johnson was a Coach's Decision-DNP for the first time all season in Game 4. Olynyk's minutes have been slashed. Jerebko was re-inserted into the rotation after he played four minutes in the first two games. Boston's frontcourt doesn't have enough room for two big men at the same time, while the Bulls can't afford to downsize.

Defensively, starting Green over Johnson allowed Avery Bradley to slide from Wade to Butler, and let Crowder go from Butler to Nikola Mirotic. These are wins for Boston, but Stevens has had to adjust in this regard as well.

Whenever Horford wasn't on the floor in Game 3, the Bulls relentlessly attacked whichever big was in the game by forcing them to guard Wade or Butler as they raced downhill off a high screen. The Celtics stayed home on three-point shooters and lived with what wound up being a small massacre on most possessions. Over the last two games, Boston's defense has allowed 95.4 points per 100 possessions with Horford on the court and 107.5 when he sits.

Stevens countered by benching Johnson, and bumping Horford's minutes up from 32 to 36. Instead of instructing their big to drop against Butler, Boston switched on most screens, including those that targeted Thomas on the perimeter. This strategy isn't perfect since there is no easy way to hide a guard Thomas' size for 35 minutes in a playoff game, but the quicker, smaller Celtics can help, rotate, trap, and recover, while Thomas does a decent job denying larger players the ball when the opposing team is clearly trying to attack him on the block. (He's really good at fronting in the post.)

With so many twists over the past eight days, it's risky to say that one side has an advantage in this series. But unless Rondo is able to re-ignite Chicago's offense and defend the piping hot Thomas for 35 minutes with his hand in a cast, or Butler has Secretariat's heart inserted into his chest cavity, it's hard to muster up much confidence for this Bulls roster.

Chicago had a serious advantage on the offensive glass over the first half of the series and, if anything, it has actually widened over the past two games. But Hoiberg showed his desperation after Game 4 by pointing out Thomas' apparently illegal need to discontinue his dribble on "every possession."

The Bulls are in a serious bind. Even after trading Taj Gibson and Doug McDermott, this team is not built to go small. Downsizing the rotation would destroy the one advantage they have and play even further into what Boston wants to do. By and large, the Bulls were designed with size and star power in mind—to control the glass and hope Butler can overcome spacing issues while he gets occasional help from Wade's isolated blips of glory. It's a questionable strategy, at best.

It's also why the No. 8 seeded Bulls barely made the playoffs and why they aren't a very good basketball team. We'll never know how Games 3 and 4 would've played out with a healthy Rondo, but, regardless, give Stevens credit for remodeling his rotation, tinkering with his defensive coverages, and for discovering a new way to attack Chicago's big men.

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