Jehu Chesson's kickoff return for touchdown ultimately set the table for what became a 38-0 thrashing and the third consecutive shutout for the Wolverines.
"It was a big momentum play," Fitzgerald said afterward. "But we've given up some momentum plays in the past and we responded to it.
"I just think Michigan's defense obviously out played our defense today and that made the biggest difference."
Appearing to be headed for a defensive slugfest prior to the start, Michigan's defense proved capable of slowing a physical, power running attack employed by Northwestern.
The Wolverines' defense allowed just 168 total yards of offense, 38 of which came on the ground, also picking off freshman quarterback Clayton Thorson on a pick six for Jourdan Lewis.
On the other side, the Wolverines executed the offensive game plan to near perfection, throwing off a Wildcat defense expecting to see differing looks that showed up on five weeks of film.
Jake Rudock finished 17-of-23 with 179-yards passing and a rushing touchdown.
"I think Jake just took what we gave him," he said. "You can't take everything away and he was able to find things. He's a veteran quarterback, he's played a lot of Big Ten games and he was smart with the ball, got it out of his hands, especially when we had some semblance of pressure.
"They're doing a good job and they've got a lot of volume in their offense so they billed in new things kind of in the first quarter of each game and obviously our guys didn't respond well.
"You can't anticipate what those things are going to be, some of those plays were off of some areas that we thought they might go."
Although making it a point to shake Rudock's hand and wish him well as the game drew to a close Saturday night, Fitzgerald isn't exactly mad about the fact his Wildcats won't see the fifth-year transfer, ever again.
"I'm absolutely ecstatic to see Jake Rudock graduate," Fitzgerald said with a smile. "He's been a thorn in our side at two institutions.
"I want to congratulate him, he's a great young man, it's good to see him graduate so we don't have to lose to him again."
The differences remain plentiful for Michigan between a 5-7 2014 team and the current 5-1 squad getting set to take the field next week against undefeated Michigan State.
According to Fitzgerald though, the Wolverines effort wasn't some sort of surprise and neither is the fact that Michigan played so well, calling Jim Harbaugh's team a "senior laden" group.
"Those great players are a year older," he said. "They're pretty good and they were pretty good last year. And they're not turning it over. That, to me, if you're writing to say that's the number one thing, they're not turning it over.
"Last year you could count on, maybe a couple. This year, they're not turning it over. That would be the biggest difference. That jumps off the tape too, they're playing smart, quarterback is taking care of the ball, not taking risks."
To a certain extent, Fitzgerald can see Harbaugh's approach and personality infecting Michigan's program.
"Like he was when he was a player, he was a player's player and now he's a coaches coach," he said. "He's from a great football family and they do a terrific job. There's a toughness, there's an attitude and it permeates throughout the entire football team."
When Michigan senior linebacker James Ross was ejected in the second half due to a personal foul penalty that included targeting, Fitzgerald stuck his hand out and tapped Ross on the helmet as he ran by.
Ross will be forced to sit for the first half of Michigan's game against Michigan State next Saturday, but Fitzgerald didn't find the play dirty in nature.
"I just wished him good luck," he said. "I'm a former defensive guy as you know. It's tough to play defense these days. I didn't see the play but I know the emphasis the officials were trying to make.
"I talked to the side official and the way he explained it to me made sense. Then obviously they look at it now but I'm assuming that young man was trying to make a football play, that's the game. It's a tough game.