Lucas, who was benched to start the previous game because Izzo was not pleased with his leadership, had 15 of his 21 points in the second half Saturday night as the Spartans pulled away and rolled to a 91-70 victory.
"At halftime, Coach told us to be more aggressive. He told me to more aggressive," Lucas said. "That's what we did. It paid off. Our defense started locking down and our offense, we just made plays. Everybody was making plays, just scoring more."
Michigan State (11-3) used its speed, depth and a 12-0 run to build a big second-half lead and win its Big Ten opener.
Northwestern (10-3, 0-2) lost its second straight since breaking into the Top 25 for the first time since 1969.
"It was a big win," said Izzo, whose team was upset by Northwestern in East Lansing last January. "We're not 20 points better than them. Tonight we were. Northwestern will be a very good team in this league."
But last year's victory was powered by 31 points Kevin Coble, who is out for the season with a foot injury and limped to the bench Saturday night on crutches to cheer on his teammates.
And the Wildcats didn't have an answer for Michigan State's quickness, versatility and depth.
Michigan State had little trouble driving through or getting behind the Wildcats' 1-3-1 defense, setting up easy baskets and jumpers. And they were able to do a good job defensively on Northwestern point guard Michael Thompson, who was held to eight points, nearly eight under his average.
"It's the second game in a row we haven't been able to stop anything," said Northwestern coach Bill Carmody, whose team lost its conference opener in overtime at Illinois on Wednesday.
"They kept getting the ball in the middle of our 1-3-1 and that can't happen."
Durrell Summers and Raymar Morgan added 17 points each for the Spartans, who shot 57 percent for the game.
John Shurna led Northwestern with 29 points, shooting 11 for 20 and tying his career scoring high.
Morgan hit a 3-pointer at the first-half buzzer to cap a 14-3 run as the Spartans took a 41-33 lead. During the closing spurt, Summers hit two from the line, Chris Allen drove for a basket, Draymond Green got inside for two baskets and Lucas canned a jumper as Michigan State showed its versatility.
Summers had 14 points in the opening half, including a pair of spectacular dunks and a pair of 3-pointers. He shot 5 for 7 and also had six rebounds.
Northwestern, averaging 10 3-pointers made and 28 attempted per game, was 5 for 15 in the opening half and finished the game 9 for 26.
The Spartans pushed their halftime lead to 13 points seven minutes into the second half as Korie Lucious hit a 3-pointer and Northwestern began to struggle from the field and the line.
Lucas then drove through the middle for a layup. And after an offensive rebound came his way after a missed dunk, Lucas hit a 3-pointer from the corner to make it 61-43 with just under 11 minutes to play. Michigan State is 20-2 in its last 22 games against the Wildcats.
Lucas said the loss to Northwestern last season was on the Spartans' mind "a little bit."
"We just played better defense and our offense was really rolling," he said. "We were having a lot of fun."
Lucas, last year's Big Ten Player of the Year, will have more fun if the Spartans keep winning. And Izzo said it's up to Lucas to keep it going.
"When he is playing aggressively and he is playing the way he is capable of playing, he is one of the best guards in the league and the country," Izzo said.