You knew it was true just by watching the games. You saw Robin's long arms tip balls away from opponents. You saw him at the front of the rim slamming back missed shots. You saw a completely different Suns team that was still scoring at an incredibly efficient rate but was also controlling the glass.
Here's even more proof:
And why does rebounding matter so much since the Suns field goal percentage defense was slightly above average before Robin started playing and got mere .005 percent better after?
Because the Suns defensive woes stem from two things that really aren't about playing defense during the shot clock. Rebounding and Turnovers.
The Suns, as we showed in this fancy chart a few days ago, are a very poor turnover team. They don't create many turnovers with their defense (ranked 26th) and they turn the ball over too many times (ranked 11th). Those combine to give opponents more possessions per game.
Rebounding woes do the same thing. When the other team is getting extra shots at the basket due off of offensive rebounds then it negates all your great defensive work.
Robin didn't impact the turnover problem but he was huge on the glass. Pun fully intended. With his presence taking away opponents 2nd chance points and give the Suns more easy put-backs....well, you know the story.
We miss you, Robin. Get well soon.