The event, headlined by Gina Carano vs. Cristiane "Cyborg" Santos for the inaugural Strikeforce 145-pound title, will air live this Saturday on Showtime.
Taylor has won his last seven fights in a row, most recently against Dong Sik Yoon in his DREAM debut last month.
Diaz missed a scheduled drug test on Friday, as well. As a result, the CSAC refused to grant him a license to fight Hieron.
In April, he told the Los Angeles Times, that he was "a cannabis user" and has "an easy way" to deal with state athletic commission tests.
Diaz tested positive for marijuana after his February 2007 victory over Takanori Gomi at Pride 33. As a result, the victory was later changed to a no decision by the Nevada State Athletic Commission.