Tomas Satoransky was roughly 92 feet from the basket when Marcus Smart sidled up alongside. Team USA was already up double digits late in the first half of Sunday’s FIBA opener but Smart wasn’t about to let anything come easy for Satoransky, the only NBA player on the Czech Republic’s roster, and thus began their tango.

Smart stared straight through a would-be screener trying to create space as Satoransky tried to dribble up the floor. Smart crouched into a defensive stance at the midcourt stripe and Satoransky gave the ball up quickly, only to receive it back on a handoff.

Smart immediately pursued then blanketed Satoranksy as he tried to maneuver right, then left, then right again. A screener came from the left wing with hopes of un-Velcro-ing the two players and Smart tried to step over a protruding leg only to be whistled for a phantom foul.

Unfazed, Smart clapped emphatically after the sequence. Team USA coach Gregg Popovich pleaded for his player. Then Smart quickly reattached himself to Satoransky’s hip before play resumed.

The sequence was a small glimpse into why Smart is on Team USA this summer. A late invite after all the big-name stars bailed, Smart missed much of training camp with a calf injury and still made enough of an impression in limited time to make the final 12-man roster. Now he’s setting the defensive tone in a tournament that typically favors offense.

Smart is a luxury for Popovich. The type of player he can deploy for the final play of overtime against Turkey and watch Smart confidently switch onto 6-foot-10 big man Ersan Ilyasova and pester him on a last-gasp 3-point attempt that would have won the game. Ilyasova used his height to get a decent shot up over Smart but it clanged harmlessly off the side rim.

That Smart is bringing the sort of First-Team All-Defense intensity to a summer exhibition should come as no surprise. He does not know how to downshift on the defensive end. And an entire world of hoopers are being introduced to his familiar brand of in-your-jersey defense.

Given that Team USA lacks the top-tier offensive firepower it typically possesses, Smart is all the more valuable in this tournament. He logged nearly 21 minutes of floor time in Sunday’s win as the Americans limited Czech Republic to 67 points on 40.6 percent shooting. Smart played only 11 minutes against Turkey but got deployed multiple times in key late-game situations when USA needed a defensive look.

While so much of the focus on Team Shamrock — Boston’s quartet that comprises a third of Team USA’s roster — understandably falls on younger players like Jayson Tatum and Jaylen Brown, and even incoming All-Star Kemba Walker, this is a particularly valuable experience for Smart, especially since he’s being tasked with injecting a defensive DNA into his team.

Smart will be asked to do the same next season in Boston, maybe even more so than in any recent year. The Celtics lost three above-average defenders with the relocations of Al Horford, Aron Baynes, and Terry Rozier. They lost defensive versatility with the departure of Marcus Morris.

What’s left is a roster that’s more offensive-oriented, particularly when you consider the “Plan A” additions of Walker and Enes Kanter. Both Tatum and Brown have the ability to be impactful defenders but must become more consistent with their defensive efforts. Smart and Gordon Hayward will shoulder a large defensive burden among the top rotation players.

Consider this: Boston lost its two top players based on ESPN’s Defensive Real Plus/Minus stat in Horford and Baynes, a duo that both ranked in the top 25 among all NBA players. The “Plan A” additions of Walker and Kanter come with undeniable offensive talent but both ranked among the bottom 15 percentile of all NBA players in defensive real plus/minus. Walker was 441st among 514 total players, while Kanter was 445th.

A glimpse at what Boston lost versus what it added on the defensive side. Defensive real plus/minus measures a players’ on-court impact on defensive performance, measured in points allowed per 100 possessions.

Scoff at Irving’s high defensive metric but it’s balanced out by how improbably low Morris ranked. Boston is left hoping that a lot of its younger faces, including rookies, can bring some defensive intensity this season.

The Celtics have lived near the top of the league in defensive rating in recent seasons, including finishing sixth in 2018-19 (107), second in 2017-18 (103.2), and fourth in 2015-16 (102.5). Only once has Boston been in the back half of the league in defensive rating during Brad Stevens’ tenure, finishing 17th in his first season.

If the Celtics are to prevent a sharp drop this year, much of that responsibility will fall on Smart. Not only will he routinely be tasked with checking the opponent’s top scorers but he could be asked to defend opponents of all sizes if Boston leans heavy on small-ball lineups.

Smart is undoubtedly ready for that challenge. And he’s already insisted he won’t rest on his laurels after finally earning league-wide recognition with the All-Defense honor last year. “That doesn’t determine the type of defender I am,” said Smart. "Whether I got it or not, I’m still gonna be the defender I am.”

Smart’s challenge is getting everyone else to buy in, all without having the backline safety net that Horford and Baynes provided. Smart must set the tone with his play and hope that everyone arounds him picks up their own intensity.

These glimpses with Team USA are encouraging. Smart’s defensive hustle is accentuated on a stage where offense is king. It’s notable that Satoransky made only one shot over the final five minutes of the first half during Sunday’s opener and Team USA went into halftime up 14 before coasting to the finish line.

Stiffer challenges await for Team Shamrock, both in this tournament and especially when the new NBA season arrives. Smart’s defense and his ability to get everyone around him to buy in might dictate just what both Team USA and the Celtics are able to achieve moving forward.

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