Ben Simmons enjoyed a tremendous rookie season. And yet, after reaching heights previously unimaginable for NBA debutants, the Australian was brought down to earth in the Philadelphia 76ers' playoffs defeat to the Boston Celtics.

The Sixers were simply a better team against Boston when their Rookie of the Year was on the bench. With Simmons on the court, the Celtics outscored Philadelphia by 63 points. That was the worst plus/minus of any player in that series.

Simmons’s growing pains don’t dampen everything he achieved last year; every NBA superstar has been subjected to a similar experience early in their career. Although, they do bring into focus the steps needed to elevate his game.

Much attention has been paid to Simmons’ offensive struggles. The actualisation of long-held doubts over his ability to score, and reluctance to shoot from the outside --especially within a playoff setting-- offered a jarring reminder of where Simmons must improve. A one-point performance in the Sixers' catastrophic Game 2 collapse, speaks volumes about where limitations currently exist. But Simmons’ struggles weren’t isolated to the offensive end. They extended to defence, where Simmons struggled to impose his physical gifts against a shrew Boston offence.

Defensive weaknesses were striking, and they arose in areas that Sixers head coach Brett Brown foreshadowed earlier in the season. While acknowledging the sublime talents that make Simmons a tantalising defensive prospect, Brown correctly prophesied the improvement areas that were borne out against Boston.

“Ben, at times, comes out of his defensive stance,” Brown explained to The Pick and Roll back in February. “I’m always on him about playing six to eight inches lower and sitting in his stance.”

Simmons is bigger and longer than every other lead ball handler in the NBA. While this affords the Sixers many positives, it presents Simmons with a challenging assignment when defending point guards.

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This clip is the actualisation of Brown’s commentary. Simmons’ rigid defensive stance, one that is bordering on lackadaisical, means he is ill-equipped to deal with a slashing Terry Rozier. Such unassuming positioning, coupled with Simmons’ body language, caught many opponents off-guard during the regular season, Against Boston, the tables were turned and this was a wart that Brad Stevens constantly picked at.

Throughout his basketball life, Simmons has been the most physically gifted athlete, every time he stepped foot onto a basketball court. That was true also, for much of his maiden NBA campaign. He’s been an impact defensive player at every level without needing to utilise textbook positioning, or a stance that Brown described in February as a “crouched, attacking, aggressive position.” Devoid of such fundamentals, Simmons offered too much space for Celtics guards to exploit. Rozier was especially fond of these chances.

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Simmons spent 51% of his defensive possessions defending Rozier, Marcus Smart or Shane Larkin during the Celtics series, per Second Spectrum data provided to the NBA. Boston recorded an offensive rating of 120.8 during these possessions. Over half of the Australian’s series was spent defending point guards, who also double as the smallest opponent on the floor. In those moments, the Celtics scored like the best offence in NBA history.

Not all of this is on Simmons; the Sixers much-vaunted defence suffered from a team-wide malaise throughout the Celtics series. Boston also found offensive contributions from unlikely characters, as evidenced by Aron Baynes’ emergence as a floor spacer. There was however a clear nexus between Simmons’ personal performance and the Sixers defensive struggles, as Philadelphia’s defensive rating fell by 31.2 points when Simmons left the court, per NBA.com.

It is clear that if Simmons wishes to lead the Sixers' defence from the perimeter, he must quickly improve his rudimentary defensive actions. In the moments where he acts as the first line of denial, Simmons’ size can be leveraged into a disadvantage should his attention to detail wane. This occurred all too regularly against the Celtics, and serves as an intuitive data point as the new season approaches.

Simmons’ limitations as an on-ball defender are largely muted by his athletic gifts during the regular season. But when the playoffs arrive in April, scouting reports will tighten and invariably piggyback the blueprint laid out by Boston. With the Sixers looking to improve on a second-round exit, it is hoped similar mistakes will be avoided within Simmons’ postseason encore.

Simmons still has a nasty habit of ball watching on the perimeter. A fixation on the basketball is more palatable when your opponent is stationary in the weak side corner, as opposed to one that's slashing around the perimeter. While this presented less of an issue when defending the ball handler, shifty guards such as Rozier can accentuate this flaw with movement. There were moments against Boston where Simmons was frozen in the face of an accelerated defensive workload.

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There were also too many moments where Simmons made inexcusable defensive blunders. Plays like this one – where he aimlessly abandons Jaylen Brown, a 40% three-point shooter last season – were all too common.

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Once again, this speaks to Simmons experiencing the rigours of playoff basketball for the first time. During his high school and college career, Simmons could get away with loafing tendencies because of his athletic supremacy. Those days are now over. The impacts of each misstep will be amplified, especially as Philadelphia gets closer to its desired place atop the Eastern conference.

How much time Simmons actually spends defending point guards is something to watch this season. It’s a question that runs in parallel to his personal development, and that of another number one overall draft pick. If Markelle Fultz becomes a suitable option alongside Simmons - an outcome that is irrevocably tied to the potential resurgence of Fultz’s jump shot - the Sixers will have the guard depth to more readily transition Simmons away from smaller opponents.

This change of defensive assignment would play much better to his current strengths.

With Robert Covington equipped to take the primary assignment against elite wings, Simmons can be afforded time to roam away from the basketball. This is one area that he excels at, and there were glimpses during his rookie season. Simmons can almost bait opponents into making a pass when he knows he can go and pick it out of the air. He can get his hands from his hips to above his head quicker than most, and pick things out of the air with deflections or steals. These are lethal talents that will only be sharpened with NBA experience, and it's why Simmons’ defensive potential remains sky-high.

A well-timed reminder that he is a legitimate 6’10” athlete, who covers a lot of ground on a basketball court, is the continual reminder of how Simmons can grow into being an elite defender.

Greater attention to detail, focused through more NBA minutes and playoff disappointment, is the next step in Simmons' journey as a defensive player.