"Darren was basically our eighth inning guy for the most part, so those guys will have to just slide up and fill that role," manager John Gibbons said.
It was a natural decision for Gibbons, who's been impressed with what he's seen from the duo thus far in the season, and he will likely use them based on the situation at hand.
"We'll see how it all stacks up," Gibbons said. "Delabar is good against righties and lefties. Cecil is a specialist, but he can get both.
"I think [Cecil] just found his niche. He really likes it in the bullpen ... . He's just doing a great job."
Even with Delabar and Cecil seemingly up to task -- both have logged a lot of innings and lead the team in ERA out of the bullpen (1.80 and 2.25, respectively) -- Oliver's loss is substantial.
"One less valuable guy down there," Gibbons said. "He's a good pitcher for us. Hopefully it's not too long."
Evan Peaslee is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.