The boxing itself is markedly speedier than in earlier games, offering hundreds of punches over the course of even shorter games and putting a fairly heavy emphasis on the idea of counter-punching - even more than Round 4 - with just a quick flash indicating a particularly effective counter. The Cutman interface for fixing damage is still gone, replaced with a simple meter that will refill set amounts according to how much of a beating you've taken.
The actual boxing matches aren't terribly different from what was seen in Round 4. It works, and works well, adding just enough wrinkles to the formula to allow them to really gel with the increased speed of matches and particularly finicky nature of using the right stick for all the punches.
It's a kind of slowly evolving series of matches that starts out with the contact-only grading of the amateur leagues and slowly graduates to things like having to maintain a cut eye over multiple rounds or avoiding body blows because the compromised judges will call it an illegal shot all the way up to a three-stage showdown with a boxer that's much, much more powerful than even the seriously beefy Andre.