Raymar Morgan scored eight of his 14 points during a dominating first half, and ninth-seeded Michigan State clamped down on eighth-seeded Marquette in a 61-49 win in the first round of the East Regional on Thursday night.
"I don't want to just be a defensive team - basketball is a two-way game," Izzo said. "Saying that, if you can only be good at one, your chances of moving on are better if it's the defensive end."
Drew Neitzel and Marquise Gray added 12 points apiece for the Spartans (23-11), who shot nearly 54 percent and never trailed in advancing to face the North Carolina-Eastern Kentucky winner in the second round Saturday.
"It's been our mind-set the whole season to win with defense," Neitzel said. "We don't have the most dynamic weapons on the offensive end, so we've had to rely on our team defense the whole season - especially in this game."
The nation's fourth-best scoring defense held Marquette scoreless for almost 10 minutes to start the game and limited the Golden Eagles - coached by Izzo's longtime friend, Tom Crean - to less than 32 percent shooting in one of their worst performances of the season.
"It was a very difficult prep week for me," Izzo said. "Yet I'm learning that it's going to happen in this business. You're going to play your friends sometimes."
Izzo saved a few tricks for his first matchup against his close friend, with most coming on defense.
"We had some new things, but bottom line, they executed their defense game plan really well, and we didn't," Crean said. "It's not easy to chase those screens."
Dominic James scored 18 points on 6-of-16 shooting and Wesley Matthews added 10 points for Marquette (24-10). But they couldn't keep the Golden Eagles from their puniest point total of the season, falling shy of a 58-point performance in a Jan. 7 loss to Syracuse. Marquette also finished almost 24 points below its scoring average.
The Golden Eagles trailed by double figures for nearly all of the second half before pulling as close as 57-49 on James' 3-pointer with 36.5 seconds left. But it wasn't nearly enough to keep them from their second straight first-round loss.
Meanwhile, the Spartans were saved from another early exit. Michigan State lost to George Mason in the first round last year in a game that propelled the Patriots to a most improbable Final Four.
"We had some struggles at the end of last year," Izzo said. "I didn't think all year long that we really had the defensive mentality we needed to win. It wasn't all the players - I got soft."
There was nothing soft about the Spartans this time.
Michigan State's punishing defensive effort helped Izzo win his first coaching meeting with Crean, an awkward game between two tight friends who spent five years together on Michigan State's staff before Crean left for Marquette in 1999.
Their first matchup was decided early, when Marquette missed its first eight shots and was held scoreless for the first 9:40.
Marquette played without its best defender and second-leading scorer. Guard Jerel McNeal missed his fourth straight game with an injured right thumb. He wasn't expected to play, though he did sit on the bench in warm-ups with his thumb wrapped.
"Being down a perimeter defender - especially one that was voted best in the Big East - caught up with us tonight," Crean said.
Yet his absence was more noticeable on offense because the Golden Eagles couldn't have started much colder. They didn't score until David Cubillan's 3-pointer from the left wing with 10:20 left.
Meanwhile, Michigan State scored the game's first 14 points, and controlled both ends of the floor by making six of their first 11 shots.
"There was a couple of times we started helping when there was no need to help, and they'd slip to the basket for some easy layups," James said. "That kind of takes a lot out of you, especially on the defensive end."
Joseph capped Michigan State's huge spurt with a 3 from the left corner with 10:45 remaining.
Each of Marquette's first-half baskets came from 3-point range. The Golden Eagles were 0-of-8 from inside the arc and 4-of-11 from long range.
"We wanted to force them to take outside shots and limit their penetration," Neitzel said.
Neitzel, who entered with 995 career points, reached the 1,000-point mark on a 3-pointer in the opening moments of the second half.