What makes you think he didn't say it in practice?I think this team does miss having a natural leader. It's not Ingles or Conley--they're vets, but too nice. Probably true for Mitchell as well. Rudy isn't nice, but the way he went about making his comments shows he doesn't have great instinct for it. Why couldn't he just say it straight that the perimeter defense needs to improve? Better if Rudy dropped the passive aggressiveness and just called guys out--in a not-personal, constructive way of course. Think the team would respond better. "The perimeter defense needs to improve. We need more effort." I don't think anyone would get offended by that. praising one of Mitchell's biggest rivals in the league is obvious and, if I was Mitchell, that would peeve me. I wouldn't want my teammate to play games like that in the media.
That being said, doesn't seem like it was a big deal.
It wasn't like nobody knew what the problem was. It has been a focus for sometime and even the main culprits were admitting they need to play some defense. Going vanilla with stuff like "we need more effort" which has been told since the beginning of the season wasn't very effective anyways. Sometimes truths need to hit hard and what Gobert said wasn't even that hard.