It was Rees's first defeat in 28 professional bouts and compounded a bad month for trainer Enzo Calzaghe, whose WBO cruiserweight champion Enzo Maccarinelli lost his title to David Haye a fortnight ago.
"Having your own world title show is what every boxer dreams about, I've watched Joe and Enzo headlining, now I hope it's the first of many for me, " Rees told BBC Sport Wales.