"This team is playing with a ruthless defensive efficiency, combined with traditional Welsh attacking flair, " he said.

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Those teams, who all play similar styles of defense, rank sixth, fifth and first in the NBA, respectively, in defensive efficiency.

WSJ: Teams With Sharp Defense

No team has given up fewer points per possession than Louisville since 2003, when kenpom.com, the advanced basketball statistics website, started tracking defensive efficiency.

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All five clubs rank in the league's top half in either offensive or defensive efficiency, but neither rates in the top half of both categories.

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The Pacers lead the league in defensive efficiency and align themselves in a way that limits shots from the painted area and the 3-point line.

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Wisconsin ranks second nationally in defensive efficiency, behind Louisville.

WSJ: NCAA Championship: Best Team vs. Best Conference

And as if those figures aren't impressive enough, the Nets did all of that against a team that finished the regular season ranked fifth in the NBA in defensive efficiency (points allowed per 100 possessions).

WSJ: Nets Earn First Postseason Win in Brooklyn