"His calf feels good and he and [pitching coach Darren Balsley] have worked on a number of things," manager Bud Black said. "That's a good step for him."
Kelley was injured during a game against the Rockies on Wednesday and was placed on the 15-day DL on Thursday.
"Physically, he feels good now," Black said.
Kelley, who has allowed six earned runs on nine hits and five walks over 5 1/3 innings this season, said he would use the time on the DL to work on his mechanics.
He has been watching video from his time with the Yankees last season and compared it to video of his struggles in his small sample size with the Padres. He noticed a few things to work on, including keeping his front shoulder closed during his delivery.
Black said Kelley will pitch on a rehabilitation stint in Minor League games before he's eligible to come off the DL on May 7, but the team is still formulating that plan.