guys like Chris Arreola I don't think could fight 15 rounds. Even Bermain Stivyrne look completely exhausted after 8 or 9....never look so good beyond 8 rounds either and Mike Tyson certainly petered out after eight or nine rounds himself. Gone are the days or fighters could fight 15 solid rounds. Let's take a look at Rocky Marciano that monster just kept getting stronger and stronger the more rounds he fought. I think Rocky could probably fight 20 or 25 rounds no problem