"He had a little bit of soreness, and he treated it and we kept him out for a day or two," Price said. "He said he was good to go, 100 percent. But, unbeknownst to us, he had some sensation in there that wasn't debilitating and didn't prevent him from being able to play."
Eventually, it hit a critical point, and medical tests revealed the fracture. Price said the 32-year-old outfielder had been playing through whatever pain he had, in hopes of continuing to make an impression in camp.
"He wanted to go out there and compete," Price said. "He knows [there are] jobs to win on the team, and I think he really wanted to play and didn't want to make a [big] deal of it. Unfortunately, there probably were some issues, and they were exacerbated yesterday when he tried to get out of the box, I guess."
With Bourgeois, whose arm was in a sling on Sunday, out of the picture for Opening Day, non-roster invitee Brennan Boesch is among those who could be seeing more time in center field behind Billy Hamilton. Hamilton was back in the lineup on Sunday after some shoulder problems of his own.
Boesch has logged exactly one inning of work in center field in the Majors, but he had 20 appearances there last season with Triple-A Salt Lake in the Angels organization.
"I think he's looked very comfortable going into both gaps, going back on a ball, throwing," Price said of Boesch, 29. "He looks like a natural in center field."
John Schlegel is a national reporter for MLB.com. You can follow him on Twitter @JohnSchlegelMLB. This story was not subject to the approval of Major League Baseball or its clubs.