Zook has been under fire for the 1-6 start, which includes six double-digit losses. Illinois endured a disappointing 5-7 season last year after reaching the Rose Bowl in 2007.
"There will be some changes, but there won't be a change at the top," Guenther told reporters Saturday at halftime of Illinois' 24-14 loss to Purdue. "There's a great deal of frustration obviously with the program at the moment. We're still going to evaluate [at the end of the season], but I think it's really unfair to start jumping at the end of the fifth year on a guy."
Zook is 19-36 at Illinois after Saturday's loss. He received a one-year contract extension this summer that takes him through January 2014.
Adam Rittenberg covers Big Ten football for ESPN.com. He can be reached at firstname.lastname@example.org