They ended up losing 37-34 on an Illini touchdown with five seconds left.
The thrilling comeback win clinches bowl eligibility for the Fighting Illini under Smith, and represents the best stretch of Smith's collegiate career to this point. The Spartans dominated the first quarter with 28 points, but, this dominance did not keep up all game.
While Michigan still has to take care of business this Saturday to truly revel in MSU's misfortunes, the fact that it's now 4-5 and limping into the game does add an extra level of revelry for the week. Noise from Michigan State's defense, but also from fans in the Spartan Stadium stands behind the IL sideline.
The reprieve was only temporary for the collapsing Spartans.
But Illinois stayed alive with an 83-yard TD pass to Imatorbhebhe with 14:48 left and a 76-yard interception return by safety Sydney Brown with 4:53 left.
Michigan State's Matt Coghlin kicked a 46-yard field goal with 3:17 remaining to make it 34-30.
IL converted a fourth-and-17 with 1:55 remaining in the game on a 37-yard deep shot to Josh Imatorbhebhe. The Illini finally scored with 5 seconds left. They've now forced 26 turnovers on the season, and that helped them get back in this one.
Michigan State: It was simply an appalling loss for the Spartans, who have now dropped four straight as their season has gone from bad to worse.
They get an bye week before traveling to No. 18 Iowa on November 23.
Michigan State: The Spartans play at rival Michigan on Saturday.