Right-hander Eric Hacker, who was tentatively scheduled for spot start duty before pitching 3 1/3 innings in relief of Francisco Liriano on Wednesday, was optioned to Rochester to make room for Swarzak on the roster.
Swarzak, who made 15 starts with the Twins in 2009 and posted 4.87 ERA in four starts with Rochester this season, will start on three days' rest.
"It was better suited for Swarzak than our other options," Twins manager Ron Gardenhire said. "We had to have somebody for the second game or for Saturday, so instead of doing something silly we just wanted the second game to be one our callups."
Gardenhire also announced right-hander Carl Pavano is sick with the flu and will have his scheduled Saturday start pushed back to Sunday.
Right-hander Nick Blackburn will still start Game 1 on Thursday, and will be followed in the regular rotation by right-hander Scott Baker on Friday in Kansas City and left-hander Brian Duensing on Saturday.