ARLINGTON, Texas -- Jim Harbaugh gathered his team on Friday night and read them a letter. 

It came from Anthony Riddle, a 13-year combat veteran in the United States Marines who also happened to be a Michigan fan. 

"The reason for this letter is for the last three months, I have heard how young this year's team is," Riddle wrote. "Let me be very clear: That sort of criticism is bulls---." 

For two pages, Riddle told of his time leading a platoon of 52 Marines on three tours in Iraq before he was 22 years old. None were over the age of 20. Harbaugh's virtual and physical mailboxes are constantly barraged with mail, but Riddle's letter stood out, so he felt led to share it with his team. 

"Just to hear that letter and say, 'OK, there's 18-, 19-year-old guys going over there defending our freedom," quarterback Wilton Speight said. "Why can't we step out onto the field in Cowboys Stadium and play a simple game of football?" 

The Wolverines lost 11 drafted players, and several other starters, from last year's Orange Bowl team. On Saturday, with Riddle's letter still literally folded and tucked in his pocket, Harbaugh's No. 11 Michigan team dominated No. 17 Florida's offense for 60 minutes, stomping its way to a 33-17 win that was only competitive because Speight threw a pair of first-half pick-sixes that sent the Wolverines to the locker room trailing, 17-13. 

Mistakes like that are easier to shrug off when you limit an offense to just three points and nine first downs and get two field goals of over 50 yards from a freshman, Quinn Nordin.

"This whole season, we've got something to prove," Michigan linebacker Devin Bush said. "Young don't mean nothin'." 

Well, most of the time it does, but when Harbaugh is in charge, it seems like it means a whole lot less than it does on other campuses. 

When the Wolverines got out of their own way with costly mistakes that put Florida in the game, his pair of top-10 recruiting classes and reputation for player development shined. 

"You see guys like [freshman receiver Tarik Black]," Speight said. "He was playing in Connecticut in front of 50 people last year." 

Saturday, in front of 75,802 in attendance at AT&T Stadium, Black hauled in a 46-yard bomb to put Michigan ahead early.

Defensively, the Wolverines dominated. The Gators finished with 11 rushing yards on 27 attempts, and Michigan forced five fumbles, recovering three.

"All those guys stepping in, in their first game of college football for some of them, it's outstanding," Harbaugh said. "Really, really proud of them." 

No team in college football returned fewer starters for 2017 than Michigan. Though 10 Gators sat with suspensions -- including star WR Antonio Callaway and starting RB Jordan Scarlett -- it wouldn't have mattered much. 

"They whooped us," Florida coach Jim McElwain said, the first of four times he used the word in his postgame press conference. "Plain and simple." 

The Wolverines aren't a compelling visual specimen, but they are effective. They don't jump off the screen, but they do jump off the line, noticeably faster than an overwhelmed Florida offensive line. They harassed freshman Florida QB Feleipe Franks for the first half and sent McElwain looking to his bench in the second. When he found Notre Dame transfer Malik Zaire, the Wolverines forced nearly all of his 17 second-half pass attempts to come under pressure. 

In the final minutes, they handed him one final indignity with a sack/fumble for a touchdown, emptying the Florida side of the stadium. 

"Our defense was amazing," Harbaugh said. 

Yes, Michigan is young and inexperienced, but its talent is undeniable. And Saturday, Harbaugh's third pack of Wolverines looked nearly identical to his first and second. Michigan will be run-first and set up play-action bombs like the one Black caught and like a 48-yarder Nick Eubanks hauled in later. 

Michigan will stop the run and collapse pockets, even if it faces much stronger offensive lines as the season progresses. 

"Our guys were relentless," Harbaugh said. "Our linebackers were running sideline to sideline." 

Resetting a roster like Michigan is tasked with doing in 2017 is never easy, but, Saturday, relying on teenager after teenager didn't seem to matter.