"It came about during the rehab," White Sox general manager Rick Hahn told reporters before Wednesday's contest at Comerica Park. "It wasn't something he had mentioned prior to starting the throwing program.
"He felt a burning sensation in his elbow. A lot of times with the UCL tear, there's a specific instance where a player feels a pop, so to speak, or something specifically tear. That did not happen in this specific occasion.
"Instead, when he tried to ramp it up, he felt some discomfort which he described as burning in the area of the elbow," Hahn said. "We shut him down and tried to treat it up and started to ramp him up again, but the burning continued, at which point he was diagnosed as having a tear."
Jones, 28, faced five batters this season and yielded four runs on two hits and three walks. He seemed to be the frontrunner to replace Addison Reed as the team's closer, but was hurt from basically the start of Spring Training.
Hahn said that Jones apologized to him after this latest setback, which the White Sox general manager said clearly wasn't necessary.
"Not surprisingly, he promised that he was going to work extremely diligently to get back as quickly as he could," Hahn said. "I actually thought, although wrongfully feeling the need to apologize, he had a good mindset about it. He was ready to get the repair done and get back on his rehab as soon as possible. It's unfortunate for the kid. He's a guy with a lot of upside and somebody we thought would help us this year and next year.
"He's been through a lot going back to that first Spring Training conversation that we had down in Glendale [Ariz.] when it was first his back acting out. It's unfortunate for the kid, but given how hard he works and similarly his makeup, I know he will do everything in his power to get back as soon as he can. We're just going to have to let biology take its course here as well."
Even with these myriad current setbacks following 135 previous appearances over the last two seasons and a 3.55 ERA, the White Sox are not ruling out Jones as a long-term fit.
"For the time being, it creates an opportunity for somebody internally to step up and fill the void or potentially another item to pursue in the coming weeks and months," Hahn said.