James Shields, who dealt recently with back pain and nausea, passed a kidney stone last week as the Kansas City Royals were finishing off the Baltimore Orioles in the ALCS.

"It was excruciating pain," Shields said. "I wasn't feeling good."

Shields will face Madison Bumgarner in Game 1 of the Worid Series on Tuesday night after 11 days off.

The Royals debated starting him in the fourth game of the ALCS, but ultimately opted for Jason Vargas.

Shields underwent a CT scan to determine the source of his discomfort. By then, the team's medical staff deduced he had already passed the stone. He was still dealing with the illness early last week.