A month ago, the Tigers sent Willis to their spring training complex. The 2005 runner-up for the NL's Cy Young Award and 2003 NL Rookie of the Year gave up 21 walks in 11 1-3 innings over four starts and a relief appearance.
Detroit signed him a $29 million, three-year deal after acquiring him and Miguel Cabrera in a trade last winter with the Florida Marlins.