The San Francisco 49ers turned over a sizable portion of their coaching staff this offseason, and that included replacing defensive coordinator Eric Mangini with Jim O'Neil. The 49ers landed O'Neil after he was let go by the Cleveland Browns with their hiring of Hue Jackson.

It has been difficult to assess O'Neil because head coach Mike Pettine brought his defensive philosophy to the Browns. There was some chatter that Pettine backed off a bit in 2015, but we'll never know for certain who was involved with what. I don't this this is quite the same as the Chip Kelly-Curtis Modkins relationship now, but it's something to consider.

On Friday, during his KNBR interview, Kelly was asked about O'Neil. He did not offer a ton of details, but he gave us a few things to chew on as we move toward OTAs next week, and training camp later this summer.

Well, Jimmy came over from Cleveland, he was the defensive coordinator there. He's been in the league for almost ten years now. You know, he's an outstanding teacher. That's the one thing that really kind of, I gravitated to in terms of, I think the best coaches have the ability to get their knowledge to their players. And everything I heard about Jimmy, that kind of shown through. And that's what I've seen here in the three or four months we've been working together, I think his package is likable, it's learnable, it's aggressive, we're gonna get after the quarterback. It's a quarterback-driven league, and you have to disrupt the timing of the quarterback or you're going to get picked apart. It relies on a lot of man coverage on the back end, that's why we got a couple more corners here in the draft, to go along with the players we already have. But it's an aggressive, attacking style. The system is very learnable, and I think our players have really grasped it here in the short time that we've been together.

The teaching thing seems like something most coaches are going to want to bring to the table. Jed York and Trent Baalke have talked plenty about wanting teachers, but all jokes aside, there is certainly something to be said for that. This is particularly true when bringing in any new kind of scheme or philosophy. So you certainly need coaches that can teach what needs to be taught.

Kelly got moderately specific in discussing things like more man coverage, and being more aggressive. He said the defensive package is "likable." I don't know exactly what that entails, but coupled with his mention of the defense being more aggressive, maybe it means players can be in more of an attacking mode, instead of reading and reacting. I'm not sure, but that is one possible definition of a likable defense.