Erlin, who was obtained from the Rangers in the July 31 trade with Texas along with Joe Wieland, told Black that he's not sure when he sustained the injury.
So far this spring, Erlin has allowed two earned runs in four innings over two appearances. He tossed two scoreless innings against the D-backs on March 11.
In that appearance against Arizona, Erlin relieved Tim Stauffer, working out of a two-on, no-out situation by getting a fly ball and a double-play ball.
The Padres won't have any trouble covering Erlin's missed innings, even after sending out two pitchers -- Jorge Reyes and Cory Burns -- to Minor League camp on Monday. As Black said, the team can always pull a pitcher from Minor League camp for games if needed.