As for your receivers getting physical, both Rhodes and Captain are made for bump-n-run so there will be plenty of physicality going on regardless. Zimmer likes to use press coverage and get guys off their spot. When we are in nickle formation (Tavon being in the slot) Captain will be covering him and he is one of the best Nickel corners in the league. Your best best when in a 3 WR set is to attack the corner opposite Rhodes. Josh Robinson is our CB3 and has shown flashes of being really good but is very inconsistent. He excels in man coverage but isn't as physical and Rhodes, so if Quick (I'm guessing Rhodes will be covering Britt and Tavon/Captain in the slot) can get up in his face he may have some struggles.
All in all, I wouldn't underestimate our defense. We have always had talent on that side of the ball (now there is even more with Joseph, Captain and Barr as well as some quality depth) and now we have a real good defensive mind driving our team.
You're very optimistic. Captain Munnerlyn is not made for bump and run coverage. Josh Robinson has shown flashes of being really good? He was one of the few CBs that you could argue was worse than Cortland Finnegan in 2013. The guy allowed 85% of targets to be completed on him and the QB Rating against him was 127.0. He was awful. Awful. In fact, as I recall, there were rumors all off-season that Minnesota would cut him.
All in all, I don't think anyone is underestimated your defense. Zimmer was an effective DC but we'll see how he does as a HC. But in terms of talent, your defense isn't a strong unit. They were 32nd in the NFL last year in PPG Allowed and lack difference making players. The contention that you have talent on that side of the ball, imo, isn't true. In the technical sense, yes, you have some talented players. But as an unit? No. It's not an overly talented unit on paper. You're more or less hoping that every young question mark you have reaches their full potential. Zimmer has a great reputation but again, we haven't seen him as a HC. It's a different ballgame.
You saying that we shouldn't underestimate your defense is like me saying that you shouldn't underestimate our offense. Difference is that I recognize the Rams offense is likely average at best. And that's with my hoping that Shaun Hill hasn't fallen off significantly since 2010.
The Vikings offense is their team strength. Your defense? I'd just be hoping they don't get in the way this year. I certainly wouldn't be acting as if people should fear it...or even respect it. Respect is earned.
Just my opinion.