In the process of trying to return from early-season back surgery, Jones was participating in his throwing program when he began to feel a burning sensation in his right elbow, general manager Rick Hahn said.
A tear in his ulnar collateral ligament necessitated elbow surgery, which was performed Tuesday by renowned surgeon Dr. James Andrews. Jones is now on a 12- to 15-month recovery program, meaning that after missing all of this season, he could miss all of next season as well.
"He obviously was disappointed and he apologized to me, which obviously, as I told him, was not necessary by any stretch," Hahn said. "He promised that he was going to work extremely diligently to get back as quickly as he could."
Jones, 28, burst onto the scene in 2012 as a surprise Opening Day roster addition and went on to post a 2.39 ERA with an 8-0 record that year. He started slowly last season, finishing with a 4.15 ERA, and was considered a spring-training candidate this year for the vacant closer role, which became available when Addison Reed was traded to the Arizona Diamondbacks.
Instead, Jones struggled in the spring. He first was diagnosed with a gluteus muscle strain and then was said to have a hip issue. He opened the season on the active roster, but in two appearances, he didn't get an out while giving up a combined four runs.
He went on the disabled list, and it was discovered that a small portion of bone was irritating a nerve in his back. He underwent a microdiscetomy in which the irritating piece of bone was removed.
The White Sox had been hopeful that Jones could return this season, but the elbow injury earlier this month derailed those plans.
"The last thing you are thinking of is to have elbow injuries, especially with the back and everything," manager Robin Ventura said. "You are disappointed for him. You know the potential of him being able to come back and start over in his career and help us, all that stuff. You feel bad for him."
As Thursday's trade deadline approaches, Jones' status makes bullpen additions an even bigger priority.
"[Jones' injury] is unexpected, but at the same time, we have time to react to it," Hahn said. "While he conceivably could have played an important role for us at the back of the pen, we have time to try to address the void he leaves for the foreseeable future.
"We're not ruling him out long term. I think he will be diligent and will fight his way back, but 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."