"He came in and worked his tail off, but with the way some of these young guys were throwing, there just wasn't a spot on the Major League club for him," manager Ned Yost said. "We're still hoping that he can have enough time to hook on with another club and compete."
However, the veteran right-hander reportedly left camp with a broken left hand, apparently the result of punching an immovable object in frustration after his poor outing against the White Sox.
In two Cactus League outings, Penny surrendered 13 hits, a walk and seven runs.
Penny, 35, had been in camp on a Minor League deal after sitting out all of last season. Prior to taking off 2013, Penny had racked up a 119-100 record and two All-Star appearances over 13 big league seasons.
Penny said a tired right arm influenced his decision not to pitch last year, but he decided earlier this year that he was ready to make a comeback attempt.
"Last year, I sat out and it's something I've never done. I had all summer to myself for the first time since high school," Penny said in January after signing with the Royals. "At the same time, it's fun, but your mind drifts back and you miss that competition. I think right now if I wait any longer, I'm not going to be able to do it again so why not try?"
Penny made his Major League debut in 2000 and spent the first 4 1/2 seasons of his career with the Marlins. He played a vital role in the Marlins' championship season in 2003, going 2-0 with a 2.19 ERA in two World Series starts. He then spent the next 4 1/2 years with the Dodgers before splitting the following four seasons among the Red Sox, Giants, Cardinals and Tigers.
Penny last pitched at the big league level in 2012, going 0-1 with a 6.11 ERA in 22 relief appearances for the Giants. His last work as a starter came a season earlier, when he went 11-11 with a 5.30 ERA in 31 starts with the Tigers.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.