The Jiujitsu Philosopher: John Danaher
John Danaher is one of the deepest thinkers in combat sports, MMA, and jiujitsu. He has coached a number of world champions in MMA and jiujitsu/submission grappling (Georges St. Pierre, Garry Tonon, etc.). The recent leg lock technique renaissance is largely due to Danaher and his school.
Danaher was a philosophy PhD student at Columbia before discovering BJJ through Renzo Gracie's academy in NYC. When I was a Yale professor (in the 90s) I made trips to Renzo's for training. I don't recall Danaher (who would have been a student/instructor there at the time), but I do recall Craig Kukuk, Renzo's partner in the school and the first US blackbelt instructor.
Kukuk had played linebacker at Iowa State University (where I grew up), and we spent time talking about Iowa (a big wrestling hotbed) and the origins of jiujitsu and ultimate fighting in the US. I had trained in Japan and so knew quite a bit about the relationship between traditional Judo and BJJ. At one time I probably knew as much as anyone about the relationship between Judo, BJJ, MMA, and US folk style wrestling.