LINCOLN—Ameer Abdullah ran for a career-high 225 yards and two touchdowns and Nebraska’s maligned defense was much improved in a 39-19 victory over Illinois on Saturday.  Tommy Armstrong, starting his second straight game in place of injured quarterback Taylor Martinez, led the Cornhuskers (4-1, 1-0 Big Ten) to touchdowns on his first three series and was solid throughout.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.