Can Mecanim & Legacy animation be used on the same character?

I am still trying to get the grips on Mecanim. I also already have a developed movement system for my character which completely uses the legacy animation system. For a new character combat system I would like to use Mecanim because I’ll need to mirror every combat animation, and there are quite a few of them. I am wondering though, is it possible to use the Mecanim system alongside the legacy one in this way? Can one character use both Mecanim and the legacy system at the same time?

Yes, I do this for facial animation, and it works great. Let Mecanim control the bones assigned to the Avatar (i.e., in Import Rig > Humanoid > Configure…). Keep additional bones, since you’ll need them for the legacy system. Let the legacy system control the other bones. This works cleanly.

On the other hand, if you want to give Mecanim or legacy complete control over the entire model and switch between the two systems, it’s messier, especially if you also use IK. You can alternate between disabling the Animator and Animation components, but the state of your Animator’s animation state machine will get kind of messed up. In this case, it would probably be better to just reimport your legacy animations as Mecanim animations and put them in your state machine.