Kendrick, 33, said he injured himself Saturday throwing a ball from the outfield at Nationals Park. He is hitting .333 with four doubles, one triple, five RBIs and an .883 OPS in 10 games.
Kendrick has not played since Saturday, so he could be activated as early as April 26.
"It's like upper abdomen, lower rib cage," Kendrick said. "Hopefully it's something that's not a nuisance, but we'll see. It hasn't gotten any worse over the past couple days, so hopefully it's something that'll be done pretty quickly."
Leiter, 26, allowed one run and struck out 11 in 5 1/3 innings with Triple-A Lehigh Valley. His father, Mark Leiter Sr., pitched for the Phillies in 1997 and 1998. The Leiters could be just the second father-son duo to play for the Phillies. The first is Ruben Amaro Sr. (1960-65) and Ruben Amaro Jr. (1992-93 and 1996-98).
Leiter is 27-22 with a 3.37 ERA in 95 career Minor League games (69 starts). The Phillies selected him in the 22nd round of the 2013 MLB Draft.
Todd Zolecki has covered the Phillies since 2003, and for MLB.com since 2009. Follow him on Twitter and Facebook and listen to his podcast.