Constructing a college basketball roster generally consists of a combination of recruiting, attrition (graduation, defections, NBA draft departures) and transfers.

Another factor that is emerging is reclassification, in which top prospects graduate high school a year early to enter college. It's a trend that is upending the recruiting calendar and changing the way programs assemble their rosters.

In August, Marvin Bagley III announced he was reclassifying into the 2017 class to attend Duke, making the Blue Devils the preseason No. 1. Last month, Charles Bassey, a five-star forward in the 2019 class, announced he would reclassify to the 2018 class and commit to Western Kentucky.

"I think a lot of them are thinking, I can get to the league [NBA] a year faster," Kansas coach Bill Self said. "I think some are thinking, if I can be a freshman in college with the access to training and that kind of stuff, would I be better off postponing that a year? I think in some situations, it's a very worthwhile thought."

"I think a lot of them are thinking, I can get to the league a year faster. I think some are thinking, if I can be a freshman in college with the access to training and that kind of stuff, would I be better off postponing that a year? I think in some situations, it's a very worthwhile thought." Bill Self

Reclassifying is a more familiar occurrence in football. In basketball, it has traditionally been the domain of prospects from New England prep schools, where it's more common for students to repeat an academic year. NCAA eligibility requires prospects to have completed 16 core courses, with 10 finished by the time they enter their seventh semester of high school.

"Probably over a quarter of the population, when they do matriculate to [New England] boarding schools, they do repeat a grade," said Jason Smith, the head coach at Brewster Academy in New Hampshire. "The general population, not just athletes. They want to get into a more competitive [college]. When they come to a boarding school, the curriculum is that much more demanding. It allows them to take the next course in succession."

It meant players could repeat a grade and be a year older during the latter portion of their high school career and then reclassify back into their original class when they were ready to graduate. Players like Andre Drummond (UConn, 2011), Nerlens Noel (Kentucky, 2012), Wayne Selden (Kansas, 2013) and Noah Vonleh (Indiana, 2013) have followed this route.

Reclassifying is also common among Canadian prospects, whose academic calendar allows them to complete their core courses earlier than their American counterparts. Andrew Wiggins reclassified in 2013, moving back into his original class after leaving Canada to play at Huntington Prep in West Virginia. Jamal Murray reclassified in June of his junior season in 2015 after several months of debate, and R.J. Barrett, the nation's top incoming freshman, decided last summer to move from 2019 to 2018.

But it's becoming a popular trend for top prospects across the country.

Kentucky (Ashton Hagans, No. 20 in ESPN 100) and Duke (Joey Baker, No. 41 in ESPN 100) have each added players who reclassified into the 2018 class. D.J. Burns (No. 82 in ESPN 100) moved into the 2018 class after committing to Tennessee, as did A.J. Lawson (South Carolina) and Kevin McCullar (Texas Tech). Speculation that 2019 five-star prospects James Wiseman and Jalen Lecque would do the same has been a source of intrigue during their recruitments.

This weekend saw two more high-level reclassifications: Five-star guard Nico Mannion moved up from the 2020 class to 2019, and ESPN 100 Oregon commit Francis Okoro decided to enroll this fall instead of waiting a year.

"The year I'm supposed to be in high school, I'm using it to get better," Okoro said of his decision to join the Ducks this fall. "College workouts are way different than high school workouts. For me, development is a really, really huge thing for me. I talked to the coaches and they said if I come in, they're going to use that one year to really work with me."

Reclassification offers a mutual benefit for player and program. Departures via transfer or the NBA draft can leave coaches scrambling for players once the season ends, when much of the recruiting work is done for that year's class. It also allows programs to be creative in their recruiting. Getting a player in a year earlier than expected could let a program recruit another player in that position without as much conflict.

"With the one-and-done, your team's always sort of in transition, always trying to figure out who's going to be there, who's going to make the jump. You're always trying to develop players, help them meet their goals. You always know there are going to be holes to fill on your team." Dana Altman

Oregon coach Dana Altman has found success through reclassification prior to Okoro. Dillon Brooks committed to the Ducks in August 2014 after reclassifying and went on to become a key contributor during Oregon's Final Four run in 2017. Altman expects Okoro to make an impact this season.

"Both those young men felt they were ready for college," Altman said. "With the one-and-done, your team's always sort of in transition, always trying to figure out who's going to be there, who's going to make the jump. You're always trying to develop players, help them meet their goals. You always know there are going to be holes to fill on your team."

Reclassifying offers a quicker path to the NBA, but many players also point to the benefit of being able to work out and train against better players in a college environment.

"I felt like going into Duke, it would force me to grow quicker than any other situation," Baker said. "That played a big role into it. I'm going to be practicing, traveling, learning, in the weight room, getting better. Redshirt or not, it's a win-win for me and the team."

There's another major factor for many prospects deciding to reclassify: age. With the NBA showing how much it values room for development, players don't want to be 22 years old when they enter the draft.

"I felt like going into Duke, it would force me to grow quicker than any other situation. That played a big role into it. I'm going to be practicing, traveling, learning, in the weight room, getting better. Redshirt or not, it's a win-win for me and the team." Joey Baker

"I'm already 18. Why should I wait to graduate when I'm almost 19?" Okoro said. "For those that started school late, it helps you be in a good age. You want to be in the NBA, if you graduate high school at 19 or 20, you're still going to be the same age as juniors already. NBA always talks about age, they always talk about how young you are. It's really important to go in at a good age. I think everybody should think about it. ... The age thing just came up. You just look at it, you see some people still in high school, people are already 19, 20. It still hurts you in the draft."

"Analytics value it," one NBA executive said. "All their models are based on what's happened in the past, and in the past, usually your best players have come out early. That's why it predicts in the future, most of your best players will come out younger. ... You're enamored with the future, because you haven't seen a lot. Is he going to grow more, what's he going to do when he gains 25 pounds? You're filling in the blanks some with your imagination, and that helps the guys."

Kentucky has benefited as much as any program through reclassification, including Noel, Murray, Karl-Anthony Towns, Dakari Johnson, Hamidou Diallo and now Hagans, but John Calipari said it's not for everyone.

John Calipari has had success with players reclassifying, including Jamal Murray. AP Photo/Samantha Baker

"If you're not mentally mature enough or physically ready, why would you reclassify?" Calipari told the Louisville Courier-Journal. "Your body will tell you, and then your family should know your mind. You're setting somebody up for failure if you're mentally not ready to go into that man's world. ... Are you ready to be professional? And if you're not, get yourself ready so you can make it."

Self agreed. "In many situations, you're trying to put growing up and maturing in fast-forward, which I don't think is good," he said.

Another factor at play could be the risk of overexposure. In some cases, players and coaches think the more time scouts have to evaluate a prospect, the higher the chance they're going to poke holes in their game. The earlier a player can get eligible for the NBA draft, the better.

"When parents and AAU coaches say it to me, I interpret it as fear of overexposing their kids," an NBA executive said. "That's not really how it works. I understand what kids and parents and mentors are thinking. I get that game. What they'll try to kid themselves on is that's not the game they're playing: I'm getting my career started early so that I can make the most money."

The trend doesn't appear to be ending anytime soon, especially as long as the NBA maintains an age requirement. Talent will find creative ways to get to the NBA. Recently, Thon Maker and Anfernee Simons reclassified back a year and did a post-graduate year of high school to go straight to the draft. As the NBA deliberates over changing the one-and-done rule within the next couple of years, we might see more prospects move up a class to be in the first group that's able to skip college.

"Options are good, but certainly five years ago, you didn't see the reclass stuff like you do right now," Self said. "I don't know if it's good or bad."

But it's not for every prospect. Some will still choose their final year in high school. Kentucky commit Tyrese Maxey (No. 7 in ESPN 100) considered reclassifying and playing this season with the Wildcats, but ultimately decided to remain with his 2019 class.

"I felt like it was best for me," Maxey said earlier this month. "I wanted to go back to high school for one last year, have fun with my teammates. You work so hard your whole life, trying to make [the McDonald's] game and get those accolades. To have a chance to do that, you want to see if you can accomplish those things. I didn't want to rush into it. It was kind of abrupt. I've waited my whole life, might as well wait one more year and do the fun things you get to do as a senior."