Sizemore was supposed to replace Placido Polanco as Detroit's second baseman, but was never able to hang onto the job. After losing his roster spot to Will Rhymes out of spring training, he was recalled from Triple-A Toledo but hit just .222 in 17 games.
"We just haven't been able to get Scott over the hump offensively," Tigers president Dave Dombrowski said. "We didn't think we could go forward with that production from someone that we saw as an offensive second baseman, and we didn't think it would be productive to send him back to Triple-A."
Purcey is a player that Dombrowski has coveted all season, despite his early struggles with Toronto. The Blue Jays designated him for assignment after an 11.57 ERA in five games.
He was then traded to Oakland, where he pitched nine games with a 2.13 ERA.
"We tried to get David Purcey over the winter, and we tried to get him after the Blue Jays DFA'ed him," Dombrowski said. "That didn't work out, but we made it clear to Oakland that we would be interested in him if he became available."
The Tigers recalled second baseman Danny Worth from Toledo to fill Sizemore's roster spot, but held off announcing a move to open one for Purcey, since he will not arrive from Oakland until at least Saturday.