Christopher Diaz was ready to step up, and in his greatest exposure to date, no less.

The 23-year-old Puerto Rican was scheduled to fight Casey Ramon in the ESPN co-feature to Vasyl Lomachenko-Guillermo Rigondeaux on Saturday, but those plans are now scrapped. Partially, at least.

Diaz (21-0, 13 knockouts) will still fight in a 10-round junior lightweight bout leading up to the highly anticipated junior lightweight title bout, but it won’t be against Ramos. Top Rank matchmaker Brad Goodman told RingTV.com it will instead be against Bryant Cruz after Ramos withdrew with an “unexplained reason.”

“His personal physician didn’t feel he was fit to fight even though he passed all the tests for New York,” Goodman said. “Thank God we were able to get Bryant Cruz. He stood up and stepped up to the plate on less than a week’s notice and if he’s in shape I think we’ll get a good fight just like we expected out of Casey Ramos.”

Diaz hasn’t fought since April after he suffered a hand injury. Cruz, meanwhile, won just three weeks ago, a third-round knockout of Angel Luna. Cruz (18-2, 9 KOs) was stopped by lightweight prospect Ryan Martin in March.

“Christopher Diaz is one of our prospects,” Goodman said. “He was a ’26-pounder who’s been off for a while and that’s why he’s fighting at 130 in this fight. Inactivity hurts guys, we don’t know what to expect out of this fight because of this inactivity.”