Isringhausen was expected to pitch in the Cardinals' game against the Braves at Roger Dean Stadium. However, he complained of some discomfort in his back, a day after wearing a heat wrap on the region. He did not appear in the game, with prospect Chris Perez hurling two innings of relief in his absence.
"Right now, it's not a concern," said pitching coach Dave Duncan.
"He's got a little spasm in his back. When the spasm goes away, he's probably OK."
Duncan would not rule out the possibility that Isringhausen could pitch as soon as Monday. However, general manager John Mozeliak indicated that a more likely scenario would be for Isringhausen to wait until after the team's off-day Tuesday.
Even so, Mozeliak characterized the injury as "very minor."
Isringhausen had been enjoying an unusually uneventful spring. He had a fully healthy season in 2007 followed by an offseason in which he required no rehabilitation. The right-hander has appeared in four games this spring, pitching 4 1/3 innings with three earned runs allowed.
"He was walking around like it was all right," manager Tony La Russa said. "[We] just don't want to take any chances."
Matthew Leach is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.