The Cornhuskers, who can just about be counted on to upset a ranked opponent at home once a season, were within a point and had all the momentum.
But No. 8 Michigan State's defense suddenly kicked in, forced misses on 10 of the Huskers' next 12 shots and the Spartans used a 20-6 run to break things open in a 73-64 victory Saturday night.
"I feared it the whole time," Izzo said. "I feared it from late Tuesday night, to be honest with you."
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The Spartans' coach looked at Nebraska, the Big Ten's 11th-place team, as a possible trap game between the emotional 23-point win over fourth-ranked Michigan and Tuesday night's showdown with No. 1 Indiana.
Derrick Nix, who had 11 of his 13 points in the second half, admitted he and his teammates were lackadaisical early.
"We didn't stretch hard enough or something," he said, smiling. "We picked it up the second half. Coach told us we weren't playing like we were supposed to play."
"As basketball players, you seem to get happy with success when you get a win like that," Nix said of the Michigan game. "Our coaches do a good job with that. They hold us accountable every day. It gets tiring, but that's what we signed up for. We have to keep grinding."
The win over Nebraska certainly was a grind, but it kept the Spartans (22-4, 11-2) in a tie with Indiana for first place in the Big Ten.
"Our team is always a team that can get up for big games," Payne said. "This is something we try to work on, to get more consistent and carry on to teams we don't think are so good."
Keith Appling scored 16 points to go over 1,000 for his career, Adreian Payne added 15 points and 14 rebounds and Gary Harris had 10 of his 14 points after halftime.
Nebraska (12-14, 3-10) came into the game having defeated at least one ranked opponent at the Devaney Sports Center in 19 of the past 22 seasons, and 11 of the last 12.
The Huskers had the home crowd thinking it might happen against the Spartans. Nebraska never led but was within 41-40 with 14 minutes left after Shavon Shields scored 12 of the Huskers' first 16 points after half.
"They were energized and excited and I think they felt like they could win," Nebraska coach Tim Miles said. "I think they felt like they should have beaten Michigan State last time. But Michigan State, they've got a Hall of Fame coach, they've got a great program. That's why they're Michigan State, tied for first in the league, and they win a game like this tonight when they're a little vulnerable."
Dylan Talley, who scored 19 of his 28 points in the second half, said he thought Nebraska was poised to pull off the upset when it was a one-point game.
"Sure did," he said. "That's exactly what I thought. It turned out they made a couple more plays than we made. We felt we had the momentum, and things didn't go our way."
Izzo delivered a strong message to his players at the first media timeout of the second half.
"I threatened the guys," he said with a smirk. "I'm half kidding, maybe a quarter kidding and three-quarters telling the truth. We weren't guarding them."
Appling, who made 9 of 10 free throws, hit a couple to start the Spartans' decisive spurt. Branden Dawson followed with a 3, and when Nix hit a layup a while later, the lead was back to double digits.
Michigan State blocked a season-high 12 shots, with Dawson matching his career high with four swats, and outrebounded the Huskers 42-24.
Shields, who finished with 13 rebounds, had all 19 of his points after halftime for the Huskers.
Shields' last basket, a 3-pointer with 46 seconds left, cut Michigan State's lead to 68-61. But it wasn't enough to overcome the Spartans' big run and keep MSU from sweeping the two-game season series with the Huskers.
Appling became the 29th MSU player to score 1,000 points in his first three seasons and the 43rd overall to reach the milestone.
Ray Gallegos, averaging 13 points for the Huskers, was 0 for 13 from the field and finished with one point.
"It seemed like it got worse," Miles said. "You've got to stick with him. I believe in Ray, and it's a bad night and he's going to have a good night the next time out. You just watch."
The Huskers, in their final season playing in the Devaney Center, wore throwback jerseys from the 1976-77 season, their first in the building.
The game concluded the Huskers' Legends Weekend, with nearly 30 former players introduced at halftime and two-time All-Big 12 player Tyronn Lue inducted into the Nebraska Basketball Hall of Fame.