I can't say for sure, performance-wise, if this was the worst.
I couldn't pick up the CU game in Michigan, but did watch the Utah game (until I couldn't stand it anymore) and wasn't able to see the OU game (which, after the Utah game, didn't upset me too much).
But as far as results, this was the most disheartening, with bowl eligibility on the line, then getting rolled.
It's too early to spot trends under Rhoads, but a notable blemish is managing to provide the sole victory for a Big 12 North team (KU last year, and possibly CU this season, unless the Buffies truly have caught fire and beat KSU this week ... let's hope). (There are positive micro-trends, too)
This is a key week for Rhoads, to see if the team can bounce back. A bowl is there for the taking, plus a tie for 3rd in the North (possibly sole possession of it, if CU can give us help). Remember, a lot of experts picked ISU 6th.