"The doctors are concerned [about] what the tests look like," said Padres manager Bud Black. "It's the part of the elbow we're concerned about."
Kelly hasn't appeared in a Cactus League game since March 7. He has a 7.71 ERA over three games and 5 1/3 innings this spring.
Kelly had the tests performed by Padres doctors, including an MRI.
Reached by text message Wednesday, the young hurler said no decisions have been made on the next step.
"There's going to be a lot of discussion between Casey and Casey's family," Black said. "I assume they'll want a second opinion. We want to make sure the right course of action will occur."
Kelly will also have the benefit of consulting two Padres pitchers who had Tommy John surgery last year -- Cory Luebke and Joe Wieland. Another teammate, Tim Stauffer, was sidelined early in the season with a strain of his right elbow. He had surgery in August to repair the flexor bundle.
Kelly made his Major League debut last season for the Padres, going 2-3 with a 6.21 ERA in six starts. He came into camp last month as one of several candidates trying to win a rotation spot.
Kelly began last season with Triple-A Tucson, then missed five months with a right elbow strain. He eventually got healthy and reached the Major Leagues in August.
Kelly won his big league debut against the Braves the day he was recalled, tossing six shutout innings. A former shortstop who was converted to a pitcher while in the Red Sox organization, Kelly even got a hit that night, all while his father, Pat, a manager in the Reds' farm system, watched from the Petco Park stands.
"I'm not sure there's anything that could trump that moment," Kelly said last month.
Kelly was considered the major piece the Padres acquired in the December 2011 deal that sent All-Star first baseman Adrian Gonzalez to the Red Sox.
The young righty was limited to 66 2/3 innings last season between the Minors and Majors. Only once since he was converted to a pitcher before the 2009 season has Kelly eclipsed the 100-innings mark -- 2011, when he threw 142 1/3.
Kelly said last month that he was ready to tackle a bigger workload in 2013.
But now, it appears Kelly's season might be done even before it started.
"We think a lot of Casey and he was definitely in the mix for the rotation," Black said. "It's a blow."