Tillman will stay on schedule, throwing a bullpen session Monday and then starting Wednesday night's game against the Rays in Port Charlotte, Fla.
Right-hander Miguel Gonzalez is scheduled to start the other half of that split-squad day, taking the ball for Wednesday afternoon's game against the Red Sox in Fort Myers, Fla.
The Orioles haven't finalized the rest of their starting rotation beyond Tillman pitching on Opening Day and Ubaldo Jimenez after Tillman. But manager Buck Showalter said lefty Wei-Yin Chen will pitch in a Triple-A game on Monday rather than face the Red Sox at Ed Smith Stadium, which seemingly indicates that Chen is lined up to assume the third spot in Baltimore's rotation.
"We're still looking at some matchups the first nine games," Showalter said, maintaining that nothing is official past Tillman and Jimenez. "Trying to look at a couple things, trying to see how it might match up with looking at Detroit's projected roster and Boston and the Yankees, where there might be a slight advantage."
Adam Berry is a reporter for MLB.com. Follow him on Twitter at @adamdberry. This story was not subject to the approval of Major League Baseball or its clubs.