Kennedy left an April 27 start for Triple-A Scranton/Wilkes-Barre when he felt numbness in the middle finger of his right hand, initially diagnosed as a vasospasm.
The 24-year-old right-hander was evaluated in New York this week and doctors re-examined his MRIs, revealing the aneurysm in an artery near Kennedy's biceps area.
Kennedy will have surgery at Roosevelt Hospital in New York under the care of Dr. George Todd, the same doctor who performed David Cone's procedure on an aneurysm in 1996. There is no immediate timeframe for how long Kennedy will be out of action.
Manager Joe Girardi said that Kennedy was buoyed by the story of Cone's return in 1996 and wanted to speak with the current YES Network broadcaster.
After missing most of the season, Cone came off the disabled list and threw seven innings of no-hit baseball on Sept. 2 against the Athletics at the Oakland Coliseum before being removed at 85 pitches due to restrictions.
"I told him today, Cone came back and threw a seven inning no-hitter," Girardi said. "This guy does really good work."
A first-round selection of the Yankees in the 2006 First-Year Player Draft (21st pick overall), Kennedy was 1-0 with a 1.59 ERA in four starts for Scranton/Wilkes-Barre, with 25 strikeouts in 22 2/3 innings. He was 0-4 with a 8.17 ERA in 10 appearances (nine starts) over three stints with the Yankees last season.
Bryan Hoch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.