Zack Oliver replaces Clayton Thorson at quarterback; then Thorson returns

EVANSTON — Zack Oliver has replaced Clayton Thorson at quarterback for Northwestern in the third quarter of the Wildcats' game against Purdue.

Following Thorson's first interception of the game, with Northwestern tied at 14 in the third quarter with Purdue, Oliver, a senior, replaced the redshirt freshman for the Wildcats' ensuing drive after a Purdue punt.

There was no noticeable injury that Thorson suffered. It's unclear what the reason for the switch was, but the presumption is that it was performance-related.

Oliver completed his first two throws of the possession, one a 13-yard pass to Mike McHugh and the other a 37-yard toss to Solomon Vault. But he then threw an interception in Purdue territory.

After Oliver's interception, Thorson was brought back into the game and led a touchdown drive to give Northwestern a 21-14 lead.