The 2025 rookie class has been an incredibly pleasant surprise outside of Cooper Flagg. Kon Knueppel and VJ Edgecombe seem like stars in the making, Dylan Harper is already playing like a much more experienced veteran for the San Antonio Spurs and the Brooklyn Nets' wild five-player experiment is seemingly starting to bear fruit.
But as far as defenders go, you won't find two better names in this class than its first overall pick ... and the one of the draft's bigger surprises, from all the way back in the second round.
So who is the better rim protector between Cooper Flagg and Charlotte's Ryan Kalkbrenner? Let's dig in and find out.
The case for Cooper Flagg as the NBA's best rookie defender
To quote Flagg's draft profile on NBA.com:
""Flagg’s elite defensive versatility separates him from the rest of the 2025 class. He has the height, strength and instincts to play down low as a shot blocker, but he also has the quickness and athleticism to lock down on the perimeter. Plus, his motor never wanes on that end of the court...Flagg’s floor is higher than most projected No. 1 overall draft picks due to his defensive prowess and versatility, but if he’s able to unlock his full offensive potential, watch out.""
Recently, the offensive side of the ball has gotten Flagg into the headlines, as he's seemingly gotten over the quieter stretch that kicked off his NBA career (19.2 PPG, 6.4 RPG, 3.8 APG on the season). Over Christmas Week, Flagg picked up his averages across the board (24 PPG, 7.3 RPG, 5.5 APG), with a historic 33/9/9 line against the Nuggets on Dec. 23 — just over a week removed from becoming the youngest player to ever notch 40+ points in a game.
But under all of that flash, Flagg has proved every bit of the scouting report correct. Flagg has led all rookies in defensive rating on the season thus far (113.8), and more pertinently to this ranking, he's also held opponents to 62.6% from within five feet and 43.9% from between five and nine. He doesn't have the raw blocks of Kalkbrenner by a long shot (0.8 per game), but Flagg has weirdly become a bit underrated on the less glamorous end of the floor.
Ryan Kalkbrenner
One of the pleasant surprises of this draft class has been No. 34 overall pick Ryan Kalkbrenner, who positively leapt his way into Charlotte's starting lineup. While he's not the most prolific scorer in the world, even among fellow rookies (4.7 shots per game), Kalkbrenner's 78.7% shooting is eye-popping to say the least.
But before getting too carried away about his offensive efficiency, Kalkbrenner's true standout trait, ever since his college days at Creighton, has been as a pure shot blocker (2.7 per game in 2024-25). And that hasn't just translated into the NBA — it has almost gotten better, relative to the competition level jump.
Kalkbrenner's 1.8 blocks per game is already the third-highest average in the league, and his 6.1% block rate is just one spot behind. Kalkbrenner's positions in both of those stats eclipse some of the best defensive bigs in the game, including Chet Holmgren, Rudy Gobert and Myles Turner. Keep in mind as well that this is all while Kalkbrenner has missed his fair share of games will also putting in just under 26 minutes per night.
Where Kalkbrenner falls a bit in this debate is that, outside of his eye-popping shot blocking, opponents are seemingly just as comfortable taking the ball into the paint against him as they are against Flagg. He has allowed shooting averages of 62.3% within five feet and 44.9% from five to nine, directly mirroring Flagg's averages (62.6% and 43.9%, respectively). And that's with significantly less of his energy dedicated to the offensive side of the ball than what's required of Flagg. Still, the sheer production as a pure shot blocker isn't something that offers room for conjecture — it is simply there for Kalkbrenner, and it is frankly insane.