I can't place all the blame on Rivera, so I think its unfair to pass judgement at this point. A big part of the issue is Shula and the offense that he runs. It's simple, boring, predictable. I'd get rid of Shula before Rivera.
Another big part of issues are the men on the roster. Panthers are handcuffed with the amount of big money tied up and horrible draft mistakes from Hurney. Take a look at the elite teams in this league and look at their cap management. They spend smart and have enough cap room to go out and sign key FAs and make runs at guys without sacrificing other areas of their team.
I'm sorry but no coach you bring in can be great with this team and where the organization is right now. Its going to be 2-3 years before we will actually get to enjoy a winning team year in and year out. Get out of this cap hell and build through the draft. We already have key players on this roster to build around. You just can't keep building around them by taking 1 year fliers on washed up veterans hoping to find the fountain of youth.