St. Louis general manager John Mozeliak said Penny received an injection and could return to throwing in 7 to 10 days. The Cardinals were worried the right-hander, 3-4 with a 3.23 ERA, might be lost for an extended period after getting pulled before the fourth inning of Friday night's start.
"It was good news," Mozeliak said. "I wasn't handicapping it either way but I was optimistic and hopeful and it seemed to work."
Right-hander P.J. Walters, was recalled from Triple-A Memphis. Mozeliak said the 25-year-old Walters, who had been scheduled to start Saturday in the minors, could get a start while Penny is out.
Walters was 1-0 with an 0.48 ERA in three starts in the minors, allowing one run in 18 2/3 innings with 23 strikeouts and three walks. An 11th-round pick in 2006, he was 0-0 with a 9.56 ERA in eight games with one start last year for St. Louis and worked four innings Saturday, allowing two runs on three hits.
"He's had phenomenal success early on, and should be rewarded for that," Mozeliak said. "It happened to fall on his day as well."
Kyle Lohse was worried he might be joining Penny on the DL after a recurrence of a forearm injury that haunted him last season. Lohse won two games and was on the DL twice after getting hit by a pitch on May 23, 2009, and said it felt like the forearm was cramping Saturday.
Lohse gave up six runs in 3 1/3 innings and is 1-4 with a 5.89 ERA.
"I'm trying to battle through it out there and it wasn't working out very well," Lohse said. "It's pretty apparent when you go out there and throw the ball like I was today that you're not helping the team.
"We've just got to figure out what's going on."
An MRI exam was scheduled for Monday after a day to allow any swelling in the forearm to subside.
"He just didn't look like he was right," manager Tony La Russa said. "He fell behind a lot. I'm not sure why."
Penny hit a grand slam off Joel Pineiro to snap a third-inning tie, his first homer since 2003 and only the 11th grand slam by a pitcher in franchise history. Minutes later he threw a couple of warmup tosses before the team called a halt to his outing.
La Russa said pitching coach Dave Duncan immediately noticed that Penny's delivery was way off and "he was yelling, 'Don't throw anymore.' "
Penny said Duncan told him, "Don't be stupid."
La Russa was perturbed Friday that Penny disclosed after the game that he had injured the back in his previous start at Cincinnati, but hadn't informed the team. Penny said he felt better as the week went on and thought it was something he could "deal with."
"The first day it didn't feel that good, the second day it felt a little better and it was gradually better," Penny said. "I didn't feel it at all in the bullpen."
Mozeliak said he hadn't had a chance to speak with Penny.
"At some point I think we'll look into it," the general manager said. "But it is somewhat of spilt milk at this point and lesson learned, I hope."
Walters' infant daughter died in early April and he missed part of spring training dealing with the situation.
"It definitely has put some things in perspective, as far as everything," Walters said. "It allows me to concentrate at the same time. I've learned to focus on the things that are important at that moment, and not something that might be important in 10 years."