Casey was injured Friday night against the Cubs
while he was stretching for a throw. As John Mabry was running out an infield single in the third inning, he stumbled crossing the bag and may have clipped Casey with his hip or left elbow.
Casey took several strides toward the pitcher's mound with the ball before dropping to his knees in obvious pain. He was assisted off the field and needed help getting to the Pirates' clubhouse
before being taken to a hospital for tests.
"He had a shooting pain that was really bothering him,"
Pirates manager Jim Tracy said.
The fractures occurred in an area of the lower back where the muscles attach to the vertebrae, but the 31-year-old Casey isn't expected to undergo surgery. He was injured in his first game back
after missing three starts with a bruised rib.
With Casey out, first baseman-outfielder Craig Wilson is
expected to get most of the playing time. Wilson, even in a platoon role to start the season, had a team-leading five home runs entering the game against the Cubs on Saturday.
To replace Casey on the 25-man roster, the Pirates purchased the
contract of utilityman Mike Edwards from Triple-A Indianapolis.
Edwards, who was hitting .316 in Triple-A, was a utility infielder
last season for Tracy with the Dodgers.
To make room for Edwards on their 40-man organizational roster, the Pirates moved right-hander Kip Wells from the 15-day to the 60-day disabled list. Wells needed an operation during spring
training to repair a blocked artery and isn't expected to return
Casey, then with the Cincinnati Reds, missed the final 16 games
of last season with the third concussion of his career, also after
being injured in Pittsburgh. He was accidentally hit in the head by
Pirates catcher Humberto Cota's elbow as Cota was running out a
groundball during a Sept. 16 doubleheader.
Casey grew up in suburban Pittsburgh but had played all but six games of his nine-year major-league career with the Reds before
being traded to the Pirates during the offseason. Casey is in the
final season of a contract that is paying him $8.5 million this
Casey was off to a good start before getting hurt, hitting .312
with two homers and five RBI in nine Pirates games.
The Associated Press contributed to this report.