"But then the second day, it was when the pain was getting worse," Troncoso said.
Troncoso was placed on the 15-day disabled list with Pericarditis, which is an inflammation of the tissue around the heart. It's a malady Troncoso had for the first time in 2010 with the Dodgers, so he kind of suspected the same condition when the pain began.
Then again, any pain around the heart causes pause for concern.
"I got confused. I was worried," Troncoso said. "I don't really exactly know it was Pericarditis again. It's the same symptoms of pain of somebody having a heart attack. It's really painful, and doctors said that they didn't really know what caused it."
Having rejoined the team this weekend, Troncoso hopes to pitch again this season for the White Sox.
"I'm going to start my physical activity Monday again," Troncoso said. "I'm going to start playing catch and see how it feels, and I'm going to have a plan to throw a bullpen and go back to the game."
Scott Merkin is a reporter for MLB.com. Read his blog, Merk's Works, and follow him on Twitter @scottmerkin. This story was not subject to the approval of Major League Baseball or its clubs.