Lewerke, a redshirt freshman, had thrown only four passes this season, but coach Mark Dantonio went with him over O'Connor and Damion Terry in an attempt to boost Michigan State's sputtering offense. The Spartans had lost three straight games.
On his first passing attempt Saturday, Lewerke floated the ball beautifully to R.J. Shelton for a 33-yard gain on third-and-8.
Lewerke later threw a 15-yard touchdown pass to Josiah Price to open the scoring.
O'Connor, a fifth-year senior, had started the first five games of this season.