The plan calls for Wada to make two starts, the first being at extended spring training. He could make a second one in Sarasota or report to one of the affiliates on a rehab assignment.
In both starts, the Orioles want Wada to throw 90 pitches.
The Orioles have 26 players in camp, leaving two bullpen spots for Darren O'Day and left-handers Troy Patton and Zach Phillips.
Showalter wouldn't confirm that Brian Matusz won the fifth starter's job because he hadn't spoken to the left-hander, but that's the assumption. Also, Showalter doesn't want to lay out his entire rotation in case a pitcher becomes available on waivers.
The 25-man roster must be set by 5 p.m. Wednesday.
Outfielder Jai Miller can refuse his outright assignment to Triple-A Norfolk, but he's apparently going to accept it.
Wada will make the first of his two starts on Monday at the minor league complex at Twin Lakes Park.
"I wanted to go to Baltimore with the team, so it's a little bit disappointing, but I think the team gave me another chance to adjust to the schedule and I'll use this opportunity as much as possible to get ready for the season," Wada said through an interpreter - one of the Japanese reporters who filled in for us.
"Physically, I'm ready right now, but the manager gave me two more starts, so I would like to pitch much better games the next time when I'm going to pitch in the major leagues."
Asked if he was surprised by today's decision, Wada said, "I knew there was going to be a possibility that I was going to be staying here, but I still have a feeling that I want to go to Baltimore and help the team out.
"It's my fault that I injured my elbow and was kind of late. I missed a couple days in spring training, so I understand I have to get into game condition and work on that over here. I'm really motivated. I really want to show the staff that I will be ready by the time I go to Baltimore."
Wada believes that he would have accompanied the team north if he hadn't needed treatment for the inflammation in his elbow during the early days of camp.
"I probably would have had more games that I pitched longer innings, so I would have been ready for Baltimore if that was the case," he said.