I'll start off with a confession: This has been one of the tougher historical lists I've compiled.
The challenges were similar to those I faced in a recent column about the 20 most popular fighters of all time. Basically, I'm trying to formulate an informed judgement about the collective opinions, informed or not, of everybody else.
Even defining "underrated" has not been easy. I have included a bunch of old-timers in the early part of my list who are generally regarded as all-time greats by knowledgeable fans and writers, but who I still feel end up being underrated by almost everybody, including myself. That's simply because there isn't enough available footage (if any) to compare them even to newsreel-era fighters like Sugar Ray Robinson, Jake LaMotta or Henry Armstrong.
A lot of the names on this list are here because they have been overshadowed by their admittedly greater rivals, contemporaries, predecessors or immediate heirs.
There have been a lot of great fighters over the years, and during any given era, only a fairly small number usually manages to capture the public imagination and truly garner significant mainstream attention.
The more time I spent on Boxrec.com, the more I kept finding additional candidates, fighters who often had victories over uncontested all-time greats, who had dazzling records and were world champions (or very close to it) during the era when being a world champion meant actually being THE world champion.
Eventually, I narrowed it down to a list taken from across the gloved era, from the turn of the last century to the present day.