You won't find many clearer examples of a fighter's prime abruptly hitting the wall in their late twenties. From his professional debut through his win over Tevin Farmer, he went 31-1. Since then, he is 2-6-1 in his last nine bouts and that hasn't even been against elite opposition aside from Haney and Zepeda. JoJo is currently on a three loss skid against decent but sub-contender types, with none of this latest triplet of conquerors ranked in any org's top 15 (well, save Duarte, who is #5 in the WBA ratings at 140lbs but absent the rest). So how do you snap a streak like that? You lower your standards, considerably. This coming Saturday night, June twenty-first, Díaz is taking on Alexis De La Cruz Martínez in Tijuana. Riding his own three loss skid, the Mexican twenty-three year old is 9-6-2 overall. I'm not sure if this is supposed to be a litmus test for the former IBF super featherweight champion, to see if he's "still got it", or simply an opportunity to (literally) cut his losses and end his career on a W. Certainly if he can't stop De La Cruz Martínez - as three unremarkable opponents have managed to do in the past - there's probably not much point in the American southpaw, now a wizened 32, eyeing any higher ambitions.
You would love to sit him down and talk to him about what happened, get him to explain how he really feels about it because it is truly absurd. I do think his size and weird t-rex frame is the main part though - he did basically nothing above 130, which is where he built the record you describe and he's been getting molested basically since he stepped up to 135.
Hes also had substance abuse issues, and spent time in rehab. This content is protected IMO he clearly abused his body and it gave up on him. Hes physically closer to 40 than 30.