Machado made his rehab debut for the Class A Advanced Frederick Keys on Friday night, hitting two doubles and a triple in four plate appearances as designated hitter. The All-Star also played Saturday afternoon and went 1-for-4 at third base.
The plan is for Machado to play another nine innings on Sunday and then either stay with Frederick or go to Triple-A Norfolk. Double-A Bowie is playing on the road next week.
"I wouldn't say anything is off the table right now," Showalter said of whether Machado could play in Tuesday's opener of a two-game series at home against Pittsburgh. "We will have a pretty good idea after tomorrow."
While the Orioles' infield has already taken a hit with Chris Davis' left oblique injury, Showalter said that situation will not change the organization's plans for Machado.
"That'd be a bad reason," Showalter said. "It's a baseball decision now, as much as physical. That's the way [head athletic trainer] Richie [Bancells] and him put it. When he's had enough at-bats to come up here. This will give [Machado] close to 40 now."
Brittany Ghiroli is a reporter for MLB.com. Read her blog, Britt's Bird Watch, and follow her on Facebook and Twitter @britt_ghiroli. This story was not subject to the approval of Major League Baseball or its clubs.