Tillman experienced stiffness from the beginning of the outing and it continued to get worse as the game went on.
Manager Buck Showalter didn't want to take any chances with the 24-year-old.
"He wanted to continue, said he wasn't having any acute pain, but, [I] just didn't like the way he was describing it," Showalter said.
Tillman has thrown 153 2/3 innings between the Minors and Majors this season, which is well under his career high of 175 innings in 2010.
In 11 starts with Baltimore this season, Tillman is 7-2 with a 3.39 ERA.