In the early years of the NBA draft, a player had to finish four years of his college eligibility before becoming eligible. As a result, players like Kareem Abdul-Jabbar and 'Pistol' Pete Maravich had to play four years of college basketball before getting to the league, despite clearly being NBA-ready.
Kareem won 71 consecutive games with his high school team, a record that still stands 53 years later.
Some of the greatest basketball players ever to play the game came to the NBA straight out of high school.
The likes of Tracy McGrady, Kevin Garnett and LeBron James are prominent among those who starred for several years in the league. Moses Malone was drafted into the ABA and had a wildly successful rookie season, allowing the likes of Darryl Dawkins and Bill Willoughby to enter the draft the following year.
The following is a list of the youngest players to debut into the league. All of these players played only high school basketball before appearing for an NBA team.
5. Stan Brown - 18 years, 139 days
Back in the day, when the National Basketball Association was actually known as the Basketball Association of America (BAA), the draft rules we talked about earlier were still adhered to. However, the Philadelphia Warriors were able to recruit an undrafted player straight out of high school in Stanley Brown.
Brown had signed with the Philadelphia Sphas during his junior year of high school, and he played for them as a senior.
The 6'3", 200-pound point guard made his debut for the Warriors in the 1947-48 season at the age of 18 years and 139 days. It became clear that he was not good enough for the pros, and he was cut from their roster list after 19 games.
Brown played basketball professionally till the age of 22, even returning with the Warriors for a 15-game stint in 1951-52.
He realized that he wasn't good enough to last long as a professional, and he moved on with his life thereon.
4. Darko Milicic - 18 years, 133 days
Ah! It don't seem like it today, but 15 years back, you could put LeBron James, Dwyane Wade, Carmelo Anthony, Chris Bosh and Darko Milicic and not have people scurrying around to Google the fifth name.
The Serbian actually began his professional career at the age of 16 with Vršac-based basketball team Hemofarm.
While he didn't average a double-double like most NCAA-proven big men, there was a lot of hype about him at the time. The Pistons were an already successful team, having made the Conference Finals in the 2002-03 season, and Darko found playing time extremely hard to come by.
Milicic never matured into a truly valuable NBA player, and he found himself bouncing around the league. He was traded to the Orlando Magic, midseason, in 2006. Having finished his rookie contract, Darko signed a three-year, $21 million deal with the Memphis Grizzlies in 2007.
Further letdowns meant that he was traded once again to New York Knicks in 2009 for Q-Rich. Darko signed a four-year, $20 million deal with the Minnesota Timberwolves in 2010, but there were no improvements in his play. His final stop was with the Boston Celtics in the 2012-13 season, and he only played five minutes for them before retiring from basketball.
3. Kobe Bryant - 18 years, 72 days
Kobe Bryant is perhaps the most accomplished high school draft pick in NBA history. Having worked out with the Los Angeles Lakers in a session Jerry West describes as 'the best he'd ever seen', he was drafted by the Charlotte Hornets before being traded to the Lakers in exchange for Vlade Divac in one of the most lopsided deals in NBA history.
As the first guard to ever be drafted straight out of high school, basketball fans were uncertain as to what extent Kobe could develop in the league.
They got their answer very soon, as the Black Mamba won the Slam Dunk championship in 1997 and made an All Star team in his second season, while still coming off the bench for the Lakers.
What followed is in the history books of the NBA and out there for everyone to see, as Kobe fever took over in the years after Michael Jordan.
2. Jermaine O'Neal - 18 years, 53 days
The 6'11" forward-center was picked up by the Portland Trail Blazers in the same draft class as Kobe with the 17th pick. Mired deep in the Blazers' big man rotation, Jermaine was viewed as a bit-part player until signing with the Indiana Pacers as a free agent in 2000.
Increased playing time led to a dramatic improvement in his game, and by 2002, O'Neal was averaging 18.1 points, 10.8 rebounds and 2.5 blocks per game and was voted into the Eastern Conference All-Star team.
His post All-Star numbers of 20.3 points, 10.1 rebounds and 2.0 blocks are even more impressive, and O'Neal became a fixture in the discussion for the top big men in the league having won the Most Improved Player award for the season.
He made six straight All-Star game appearances from 2002-2007 and was thrice voted into All-NBA teams.
While age and the mileage of playing so long in the NBA caught up with him, O'Neal continued to make a positive impact wherever he played.
The 2013-14 season was his last in the league, and he finished out as one of the better big men of this century.
1. Andrew Bynum - 18 years, 6 days
He was looked upon as a big man to lead the Lakers back into championship contention in a few years and was developed with this goal in mind.
Bynum made the leap from bench player to starter in the 2007-08 season. He averaged a 13 point, 10 rebound double-double in 28.8 minutes per game that season - although he was ruled out by injuries for the second half of the season.
His best season was also, unfortunately, his last in the league, as he played 60 games, averaging 18.7 points and 11.8 rebounds.
He made the All-Star team as a starter in 2012 and was viewed as a piece of value in the Dwight Howard trade that summer. Injuries kept him off the court in 2012-13, and he signed with the Cleveland Cavaliers as a free agent in 2013.
But he clearly wasn't good enough at that point to play on and was traded to the Indiana Pacers. His spell in Indianapolis was a short, as he was cut after two games. He never returned to the league and retired that same year. A classic case of a player with immense potential with a career cut short by injury.
Did your favourite player make the list? Sound off in the comments section below!