Walker will be available to come off the DL for the team's three-game series in Boston beginning on July 11 -- just before the All-Star break.
Walker, who will turn 37 on Tuesday, said he's been pitching with pain in his throwing elbow for roughly a month, but was surprised to be placed on the DL.
"I've been pitching with it for probably about a month, just hurting," Walker said. "But the move caught me off guard; I didn't know what was going on. They were trying to get me to the All-Star break, shoot it up with some cortisone and give it a few days off, but we didn't make it, obviously. They had to make a move, and I don't blame them."
Walker last pitched Wednesday, striking out the one batter he faced in the Orioles' 7-4 loss to the Cubs, and refused to say that the pain in his elbow hindered his pitching performance in the past month.
"I don't make any excuses," Walker said. "I'm not a happy camper about it, but I don't make any excuses. It just hurt more and all that. I go out and just compete with what I've got. That's just an excuse for somebody. I'm not that guy."
"When I talked to him [Monday], I said: 'There's a difference between being hurt and having pain in your arm,'" manager Dave Trembley said. "I believe he was hurt, and I believe he was hurt for a while and didn't say anything. He has not had elbow problems before, he had shoulder problems before."
Walker said the inflammation was caused by what he believed to be arthritic spurs in his elbow, likely just caused from wear and tear on his body.
"If you go into anybody my age that's been pitching, they're going to have spurs, or some form of something," Walker said. "Hopefully after I get the [cortisone] shot today, a few days later I'll start throwing again and get it rolling."
Despite the move, Walker seemed optimistic that he will be back into form after the All-Star break, if not sooner.
"I was hoping to get to the All-Star break, get some drugs in me ... and come back in the second half," he said. "That's my goal still."
Amanda Comak is an associate reporter for MLB.com This story was not subject to the approval of Major League Baseball or its clubs.