Gobble was placed on the Royals' 15-day disabled list with a back ailment on Tuesday, less than 24 hours after he was charged with 10 runs in one inning in a 19-4 loss to the Detroit Tigers.
"As a player you want to pitch through things and you think you can get through the pain and keep grinding, but it's come to a point where it's time to take some rest and get this problem resolved," Gobble said.
"My back and my hammies have been bothering me for a while."
Right-hander Joel Peralta, who had been optioned to Triple-A Omaha on Monday, was immediately recalled to replace Gobble in the bullpen.
The left-handed Gobble, largely a success last year in his 74 games, has struggled most of this season. In 31 games, he held an 0-2 record and an 11.31 ERA, with opponents hit .318 against him.
Hillman said he was relieved that Gobble finally said something about his aching back. He didn't press Gobble about the length of his discomfort.
"He feels bad enough as it is and I didn't want to hit him over the head and say, 'How long has this been happening?' but if I had to guess, based on his performance, I'd have to say it's been nagging him for a while," Hillman said.
Gobble admitted the pain really kicked in during the Tampa Bay series a few days before the All-Star break. He hoped four days of rest would cure what ailed him. It didn't.
In his first outing after the break at Chicago, he faced three batters, walking two and hitting one. Then came the 10-run ordeal during which he gave up seven hits, walked four, and made a wild pitch while getting just three outs over two innings.
Finally, Gobble felt obliged to fess up.
"You don't ever want to say anything, and I take pride in not being hurt," he said. "I take a lot of pride in being out there every day and being ready. That's what bothers me most about having to go in and say something, because I'm not an excuses kind of guy."
Gobble said the pain is not in the same area where a bulge was found in his back two or three years ago.
"It's actually tightness in the hammy that leads up to the lower middle of the back," he said. "It's really just a bad back -- real sore, real tight -- and it kind of flares up here and there."
Hillman said he would not have left Gobble on the mound to throw 45 pitches, thus preserving others in the bullpen, if he knew he was hurting.
"I'm thankful he said something because if he'd continued to try to pitch through it, he might have run the risk of doing further damage," Hillman said. "Right now we don't project this to be anything major but, nonetheless, it is affecting his performance."
Gobble refused to let the 10-run ordeal get him down.
"I gave everything I had and walked off that mound with my head up," he said.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.