"It was a little scary. It got him in the head," said Baltimore manager Sam Perlozzo. "He seemed to be fine, but they're just doing some precautionary tests."
Walker underwent a CAT scan, which revealed a minor concussion. He's listed as day to day.
The incident happened during a fairly routine round of live batting practice. Walker was matched up against right fielder Nick Markakis, who had just stepped into the batter's box a pitch or two before. Markakis drilled a line drive back through the box, and Walker turned away from the ball but got hit directly in the back of his head.
"I think it was an offspeed pitch," Markakis said. "I saw it going right back up the middle, but everything happened so quick. It shocked me, pretty much. You hate to see something like that happen."
Walker never left his feet, but the shot elicited an audible gasp from the fans behind the first-base dugout. The team's trainers converged on the mound to check on Walker, and moments later, they walked him to the clubhouse. Walker had been pitching without a protective screen, which may have stopped the ball short of impact.
"It's optional for the pitcher," Perlozzo said. "Some guys don't feel like they can throw the ball properly with the screen in front of them. If they want it in front, they can put it there. If they don't, they can take it away."
"It definitely made my heart skip a little bit," added Markakis. "You hate to see something like that happen. Hopefully, he's OK, and we can get him back out there as soon as we can."
Walker, who signed a three-year deal for $12 million this winter, is one of the key pieces of Baltimore's rebuilt bullpen. The Orioles will monitor his progress before allowing him to return to full workout duty.
"He said he was a tough son of a gun," Perlozzo said. "That's what he said when I got there. I believe him."
Behind the mask: Veteran backstop Paul Bako, the favorite in the race to be Baltimore's backup catcher, has been impressed by the quality of the team's arms in the last two weeks. The 34-year-old has caught for eight different big-league teams, so he's been around long enough to spot a quality staff when he sees one.
Bako said he's been most impressed with starters Daniel Cabrera and Adam Loewen.
"Not to put any pressure on those guys, but if Cabrera and Loewen step up a little bit -- and just mature in a natural progression, not adding on a whole lot -- it's really going to deepen our pitching staff and give us a real chance in the [American League] East," he said. "Our position players obviously speak for themselves, and with the additions to the bullpen, there's really no reason we can't [compete].
"If our starters stay healthy and give us the innings, there's no reason at all we can't compete for a title in the East."
Drill sergeant: Perlozzo presided over several drills Friday, including a morning workout on rundowns. The manager said his team's energy level has been good for the first week of full-squad workouts.
"I thought it went pretty well today," he said. "You're going to have a few glitches here and there, but overall, I thought the guys put a good effort in. I think we got our point across in how we want it done."
Perlozzo also said his team seems to have a good dose of chemistry and camaraderie for early in the camp.
"It looks like they all get along good," he said. "We've got some veteran guys that are professional and going about their business, leading our young kids on the field and building up to something we want to see on Opening Day."
Quotable: "We're out there getting players from everywhere these days. It just makes it a little tougher to learn the languages. Before you know it, that will be one of our prerequisites -- one of our coaches will have to speak French or Japanese." -- Perlozzo on the four Canadians in Baltimore's Spring Training camp
Spencer Fordin is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.