Snippet from the article

Frank Martin had a ringing endorsement about his former player’s defensive I.Q.:
“Sin’s just — I haven’t had a guy that completely understands everything that we do since I’ve had Jacob Pullen at K-State — the way Sin understands. He knows every defensive concept from all five spots. I don’t have to practice him at the 5. If I told him to play center, he’d understand everything he’s supposed to do at the center spot.” (via SEC Country)

It’s much easier to explain the steady improvement in defensive efficiency after reading that. Not only did he improve his defensive rating from 105.9 as a freshman to a stout 88.8 by graduation, but his defensive rebound percentage took a quantum leap too. In his first three seasons, his defensive rebound percentage hovered around 12 percent. Last season it shot up to 16.1 percent, per Sports-Reference.
Thornwell is well aware of what his role will be. Here is what he had to say to USA Today:
“I’m not a lottery pick, but I feel like I’m a lottery player,” Thornwell said. “I’m a glue guy. I can come in right away and produce on both ends of the court, but most importantly, the defensive end.”