Across a range of reputable advanced statistical measures, Derrick White generally ranks among the top two defenders at the guard position among starters in the NBA this season. One such defensive ranking (Defense EPM) ranks Derrick and Marcus Smart as the leading guards (in that order). I'm excluding Gary Payton II from the ranking (17.5 mpg) and only including guards playing starter or 25+ mpg.
In the playoffs, Derrick has continued, perhaps even improved his stellar defensive play. He is playing far more aggressive on ball defense and is increasingly paired with Marcus Smart providing the Celtics with a stifling perimeter defense.
There's little argument that Marcus Smart is a great defender. He is generally more disruptive in the passing lanes and on ball than Derrick and has the better ability to defend postups of bigger players (though Derrick is no slouch). However, Derrick also rivals Marcus in shots contested, is very difficuilt to beat in isolation, and is the better shot blocker. An argument can be made he's a better help defender. In fact, I'd argue that his defensive impact rival's Smart's.
Smart will undoubtedly receive 1st team honors at the guard position this year. Other prospects for the four guard positions include Alex Caruso, Dillon Brooks and players nominally entered in previous years as guards, Thybulle and Jimmy Butler. Jrue Holliday is excellent, but hasn't been as consistent this year on defense. Could Derrick possibly sneak into 2nd team honors?