Is it biased to say that Mike and Tony are awesome? Because they are. Sure, they stand on the periphery of Denny's life, but when they're in the plot, they're awesome. Mike, a coworker of Denny's, is there for him when Eve is sick, he takes care of Enzo, and basically he and Tony act as support systems for Denny.
They're also the perfect balance of supportive and sympathetic, without going too far. When Denny comes back from the police station after being slapped with rape charges, Mike and Tony tell him, "You don't have to talk about what's going on. But it's good to talk. You can't keep everything inside. It's not healthy" (35.11). When Denny tells them he doesn't want to talk, they relent, but not after making sure he'll be okay and reminding him that their phone is on if he needs anything at all. They just want to make sure his head's not going to explode out of stress.
Not that we think that can happen, but it doesn't hurt to be careful.
This is the type of friendship that is always good to have. We can tell that Mike and Tony genuinely care about Denny and want to help him however they can, but they also want to respect his space and his needs. They teach Enzo, even in a secondhand way, that family doesn't just have to be the people who live with you. Family extends to everyone who cares about you.
Like we said, Mike and Tony are awesome.