Ponson was designated for assignment June 6 despite a 4-1 record and 3.88 ERA for a starting rotation beset by injuries and among the worst in the majors. General manager Jon Daniels has said Ponson was dumped "for disrespecting teammates and club personnel."
Diamond was optioned to Double-A Frisco, where the right-hander has already made five rehab starts. The former first-round pick is 1-1 with a 6.23 ERA in those starts. He missed all of last season after elbow ligament replacement surgery.