Hardy, who was hit by Cardinals starter Lance Lynn's fastball in the bottom of the fourth inning on Sunday, will be eased into baseball activities after the four-to-six-week healing period. His injury comes at a time when the O's are also missing Chris Davis, Darren O'Day, Zach Britton, Mike Wright and Ryan Flaherty.
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"I didn't know it would be broken. It was definitely sore and it hurt, but I didn't know it would be something broken," said Hardy, who had a CT scan on Monday that confirmed Sunday night's X-ray findings.
"It's a small bone and non-displaced fracture."
Without Hardy up the middle, the Orioles can go with Ruben Tejada or purchase Paul Janish's contract from Triple-A Norfolk. Hardy, who was in a soft cast, will meet with a hand specialist on Tuesday.
"I felt like I was making strides [at the plate], getting out of the funk I was in," Hardy said. "And then this happens. So, very frustrating."
Brittany Ghiroli has covered the Orioles for MLB.com since 2010. Read her blog, Britt's Bird Watch, follow her on Facebook and Twitter @britt_ghiroli, and listen to her podcast. This story was not subject to the approval of Major League Baseball or its clubs.