I think you're significantly overstating things and are wrong when you say he did it
"single-handedly" Blazer defensive rating & ranks under Stotts
2012-13 109.2 - 26th (Stotts 1st year; JJ Hickson C
2013-14 107.4 - 16th (Lopez + Aldridge + Batum/Matthews)
2014-15 103.7 - 10th (Lopez & Kaman)
2015-16 108.0 - 20th Big Roster Change; Plumlee + Davis + Aminu/Harkless)
2016-17 110.8 - 24th (Plumlee traded for Nurkic BUT Ed Davis hurt plays half a season)
2017-18 106.4 - 8th (Nurkic PLUS healthy Ed Davis & Aminu/Harkless/Turner/Napier +Zach)
2018-19 110.5 - 16th (Ed Davis gone; Curry for Napier; Nurkic + 2nd year Zach)
2019-20 111.9 - 20th (Whiteside & all the 7 dwarves)
if Nurkic was so transformative on defense, the Blazers wouldn't have give up 4.1 more points/100 and dropped from 8th to 16th last year. Everything else was the same...except no Ed Davis. I'm seeing that just one time was Portland not in the bottom half of the league in defense. And that one season was when everything was firing on all cylinders. They had Nurkic, Aminu, and Harkless on the front line as starters. And they had the tag team of Ed Davis and Zach as the 2nd unit. That was good defense. But they only had that one year
in other words, I think you're giving too much credit to Nurkic for that defensive success. Last year, with Nurkic and Zach, two guys a lot of people here say are great defenders, Portland had it's 3rd worst defensive rating in Stotts' tenure. Yeah, the NBA is changing, but just 4 years earlier Portland allowed almost 7 less points per 100 possessions.
don't get me wrong, I'm not saying Nurkic isn't good defensively. I am saying there's some exaggeration about how good his defense is