"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 are expected to give Ruben Tejada the bulk of the playing time at shortstop. While Orioles manager Buck Showalter moved Manny Machado over from third base when Hardy was sidelined with a foot injury last year, that won't be the case this year, as Showalter said he preferred to keep Machado at third.
The team will also add an infielder to the roster.
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."