"I'm still young," Collins said. "I'm 26."
Collins said he began feeling soreness two weeks ago in the elbow area.
"A lot of what I was feeling was normal in this stage of the process," Collins said. "It's kind of hard to differentiate that [soreness] from pain."
Collins threw a live batting practice session about 10 days ago and said he was "really sore" after that. He then went home to be with his family for the birth of his second daughter.
"It turned out that was a good break, I thought, just to rest," Collins said.
Collins came back to camp late last week, and the soreness persisted. He had an MRI on Tuesday.
"I was just at a point where I didn't want to keep pushing through it, so we opted for the MRI," Collins said. "We were hoping we wouldn't find anything, hoping it was just inflammation. It ended up being more than that. So we're back to square one.
"It's frustrating. Obviously you don't want to have to go through it twice. You can't change anything. You just go at it the same way I did the first time."
Collins' first surgery was performed by Dr. James Andrews.
Collins signed a one-year, $1.475 million deal last fall. The Royals do not insure one-year deals, a source told MLB.com.
Jeffrey Flanagan is a reporter for MLB.com. Follow him on Twitter at @FlannyMLB. This story was not subject to the approval of Major League Baseball or its clubs.