"I felt a pop in my elbow," Liriano said.
He'll have surgery on Wednesday in San Diego, with team physician Dr. Heinz Hoenecke performing the procedure.
The Padres are hopeful that Liriano can start hitting in six months, and will be able to play in the Arizona Fall League and the Dominican Winter League in nine months.
"It's a bummer," said Padres manager Bud Black. "He made great strides last year."
Liriano had a .280/.350/.417 line last season between Class A Lake Elsinore and Double-A San Antonio. He had 44 extra-base hits, 61 RBIs and 32 stolen bases in 127 games.
Liriano followed that performance by hitting .319 in the Arizona Fall League, with four home runs and 15 RBIs in 22 games. He then went and played in the Dominican Winter League.
"It's really bad, but I'll be OK," Liriano said. "I'm prepared to work hard. I'll be ready for next year."
Liriano would have likely started the season with San Antonio, though the Padres wouldn't have been at all surprised if he moved fast through the system.
"He was coming off a real strong [Arizona] Fall League, was in great shape and he might have had a chance to see San Diego by the end of the year," said Padres director of player development and international scouting Randy Smith.
The Padres have several position players who have undergone Tommy John surgery, including outfielder Chris Denorfia, first baseman-outfielder Kyle Blanks and catcher John Baker. There is no hard-and-fast timetable for projected return.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.