Kelly Bryant opened up college football's version of Pandora's box when he left Clemson before playing more than four games in 2018, which thus allowed him to play elsewhere in 2019 with another season of eligibility.
It was our first up-close-and-personal glimpse into the transfer-portal world that has now affected nearly every FBS team. It was also the first major move that had ramifications for a Power Five team, and it was even bigger news since it involved a contender that ultimately won the national championship.
So, which quarterbacks are likely to pull a Bryant in 2019?
Several guys (such as Virginia Tech's Josh Jackson and Texas A&M's Nick Starkel) already are in the transfer portal and likely won't be with their current teams at the beginning of the season, so they don't count. Others, such as Jalen Hurts (Oklahoma) and Tate Martell (Miami), already have found their new homes.
Let's take a look at some of the candidates who may make it through the spring and to the 2019 season with their current teams, but could leave that same program by the end of the year.
Feleipe Franks, Florida
Florida quarterback Feleipe Franks is one of college football's most intriguing transfer candidates in 2019.
While Franks appeared to be in danger of being benched late in 2018 before backup Kyle Trask suffered a season-ending foot injury in practice, he closed out the season and was impressive. The 6'6" rising junior wound up completing 58.4 percent of his passes for 2,457 yards, 24 touchdowns and six interceptions while running for 350 yards and seven scores.
Following Florida's 38-17 loss to Missouri in early November, head coach Dan Mullen re-opened the competition for the starting quarterback job, according to the Orlando Sentinel's Edgar Thompson, but Trask suffered his foot injury shortly thereafter. Between Trask, 4-star 2018 prospect Emory Jones and 4-star 2019 prospect Jalon Jones, Franks may face no shortage of competition heading into this coming season.
Look for Franks to hold the job throughout the spring, but Emory Jones is going to be impressive. After early games against Miami, Kentucky and an improved Tennessee, it's possible Mullen shakes things up.
Franks is talented, but he isn't the best fit for Mullen's scheme. As a result, he could become a huge name on the transfer market.
Alex Hornibrook, Wisconsin
If history is any indication, experience will work in Alex Hornibrook's favor as he enters his senior year at Wisconsin.
Like most college coaches, Badgers head coach Paul Chryst leans on upperclassmen early in the season. Although Hornibrook had a forgettable 2018 season, completing 59.5 percent of his passes for 1,532 yards, 13 touchdowns and 11 interceptions in nine games, he'll likely get the benefit of the doubt heading into 2019.
But given the upgrades in Wisconsin's quarterback room, he figures to have a short leash.
The Badgers finished 8-5 despite high expectations and a preseason Top 10 ranking, and this likely will be star running back Jonathan Taylor's final year in college. The Badgers need better quarterback play to battle for what looks like a wide-open Big Ten.
Rising junior Jack Coan fared well in Hornibrook's place while he was injured, completing 60.2 percent of his passes for 561 yards with five touchdowns and three interceptions in five games. As such, one of Wisconsin's receivers believes there will be a battle for the starting QB job.
"I definitely know there's going to be some competition for the position," receiver A.J. Taylor told Zach Heilprin of The Zone. "We've kind of seen it just throughout this season. This spring, it's going to be a time for the coaches to figure out—and the team to figure out—who's going to be that guy that takes us to the next level."
Joining Hornibrook and Coan will be Graham Mertz, a 4-star quarterback who's the third-ranked pro-style quarterback in his class. He tossed five touchdown passes in the Army All-American Bowl and looked like a star in the making.
Wisconsin has too much talent for Hornibrook to hold down the starting spot for the entire 2019 season. And if he gets benched, he could bolt to salvage a final season somewhere else.
Brian Lewerke, Michigan State
Michigan State's Brian Lewerke is another Big Ten quarterback who seemed to be on the cusp of a major leap before he flopped in 2018.
Lewerke threw 20 touchdowns and seven interceptions as a sophomore, but in 11 games this past season, he threw for only 2,040 yards, eight touchdowns and 11 interceptions. He also completed only 54.3 percent of his passes while battling a nagging shoulder injury.
As the Detroit Free Press' Shawn Windsor wrote, "If MSU wants to make a push in the Big Ten East next season, he'll have to build on what he did as sophomore, and put his junior year in the dustbin."
What if the Spartans go in a different direction?
Rising sophomore Rocky Lombardi got some meaningful snaps in 2018, but he completed only 44 percent of his passes for three touchdowns and three interceptions. Sure, he was a fan favorite and had some impressive moments, but does he project as a quality Big Ten starter?
Peyton Thorne is the only signal-caller in the Spartans' 2019 class, and it's unclear whether he's ready for live action. The better wild-card option is redshirt freshman Theo Day, who is a promising prospect.
Lewerke may be the starter as of now, but Michigan State can't keep trotting him out there if he plays like he did last season. If he doesn't mesh well with new offensive coordinator Brad Salem, a change of scenery may suit Lewerke.
Darriel Mack Jr., UCF
Central Florida's Darriel Mack Jr. has a ton of talent, but he might get lost in the shuffle of quarterbacks at his school.
Mack was thrust into the starting lineup when McKenzie Milton suffered a gruesome, season-ending injury in the regular-season finale against South Florida. He went 19-of-27 for 348 yards, added 59 rushing yards and accounted for six touchdowns against Memphis in the AAC title game, but he went only 11-of-30 for 97 yards and a touchdown against LSU in the Fiesta Bowl.
Mack's future looks bright despite his struggles against LSU, but will it come in Orlando? Former Notre Dame quarterback Brandon Wimbush has enrolled in classes at UCF and will finish his career with the Knights.
Whenever Milton recovers—which, based on Wimbush's transfer, doesn't seem likely by the beginning of the 2019 season—that will leave Mack as a backup for another few seasons at least.
Mack's future is too exciting to waste on the sideline. UCF head coach Josh Heupel has a lot of talent in his quarterback room, especially if Milton can come back and be the Heisman Trophy candidate he was before his injury.
If that happens, one can only wonder how long Mack will wait.
He still could have a redshirt season if he goes elsewhere, so he's one to watch early in 2019.
N'Kosi Perry, Miami
N'Kosi Perry has a ton of talent, and he occasionally sparked a mediocre Miami team as a redshirt freshman in 2018, completing 50.8 percent of his passes for 1,098 yards, 13 touchdowns and six interceptions. He can also do damage with his feet, although he has yet to showcase that much in college.
However, Perry also has been in trouble a few times, most notably for posting a sexually explicit video on Snapchat, according to Josh White of Miami's student newspaper, The Miami Hurricane.
Will new head coach Manny Diaz and offensive coordinator Dan Enos put up with distractions, especially with a rapidly growing quarterback depth chart?
With Malik Rosier having graduated, Perry has the most experience returning in 2019. However, redshirt freshman Jarren Williams has a ton of potential and doesn't have the same off-the-field baggage as Perry. He is more of a dropback passer with some athleticism, and he could be a steadier option than Perry, who has a history of being erratic with his throws.
Things get even more interesting in 2020, when Ohio State transfer Tate Martell will become eligible. The duo of Williams and Martell boosts the future profile of a position that has been troublesome in recent years for the Hurricanes.
Rising redshirt sophomore Cade Weldon doesn't seem like a threat to start, but if Williams overtakes Perry, the latter may look at 2020 and realize he missed his window to seize the starting gig. If that's the case, he may probably look to transfer elsewhere.
Perry will have plenty of options, but the Hurricanes may not be the best spot for him moving forward.
Unless otherwise noted, stats courtesy of Sports Reference and CFBStats.com. All recruiting information is from 247Sports, and rankings are from 247Sports' composite.
Brad Shepard covers college football for Bleacher Report. You can follow him on Twitter @Brad_Shepard.