by Steven Marrocco – MMAWeekly.com
Joe “Diesel” Riggs will not fight Nick Diaz for the first-ever Strikeforce welterweight title at “Carano vs. Cyborg” on Aug. 15 in San Jose, Calif.

Strikeforce Director of Communications Mike Afromowitz confirmed the news to MMAWeekly.com Friday morning.

Word of the change first appeared Thursday night on graciefighter.com, a website owned and operated by Diaz’s manager Cesar Gracie.

The report indicated that Riggs had withdrawn from the fight when he had an adverse reaction to a prescription medication, prompting a hospital stay that could be weeks long.

Afromowitz was unaware of Rigg’s condition and was still trying to contact the fighter.

The fight was the second title match on the Aug. 15 event to encounter problems. Alistair Overeem, who in June canceled a scheduled title defense when he injured his hand in a nightclub brawl, bowed out of a second title booking against Fabricio Werdum when he was unable to recover from the injury. Strikeforce officials are currently looking for a replacement.

Riggs defeated Diaz at UFC 57 in February 2006, and later brawled with the Stockton native at a Las Vegas area hospital. Bad blood has remained since.

Afromowitz said the search was on to replace Riggs, but gave no names of fighters under consideration.

There are now two title fights remaining on the card. In the evening’s headliner, Gina Carano will take on Cristiane “Cyborg” Santos for the first ever Strikeforce women’s 145-pound title, and Gilbert Melendez will rematch lightweight champion Josh Thomson.