Willis, out since hyperextending his right knee slipping off the mound in an April 11 game against the White Sox, threw without health issues, according to head athletic trainer Kevin Rand. He threw to live hitters last Saturday and looked impressive by all accounts.
Tuesday's session was meant to act as an in-between session between starts -- one simulated, the other real. The real one is scheduled to come on Friday, likely at Triple-A Toledo, where the Mud Hens will be hosting Rochester. Willis and the Tigers will make the decision when he's ready.
Willis, on the disabled list for the first time in his Major League career, is expected make at least two Minor League starts to make sure he's ready before coming back to the Majors. At that point, the Tigers will have to clear a spot in their rotation. Armando Galarraga has two wins and a no-decision in Willis' place, and the Tigers have won all three of his starts.
Jason Beck is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.