Armstrong was 8 of 13 for 135 yards.
Just as big as Armstrong's performance was that of Nebraska's defense, which had been one of the nation's worst through four games.
Illinois (3-2, 0-1), which came in averaging 40 points a game, didn't score its first touchdown until the middle of the third quarter. Twice when the Illini looked as if they would make a game of it, the Huskers made big stops.
Josh Ferguson led the Illini with 114 yards on 19 carries and another 82 yards on eight catches.