or Potentially great

Mashburn AKA Mosnter Mash, still my favorite Heat SF of all time even though Lebron is a far better player with all respect due to Lebron and Glenn Rice
SN: I still have nightmares of that runner shotcomplex.com said:25. Greg Oden
Career years: 2007-present
Career stats: 9.4 PPG 7.3 RPG APG SPG 1.4 BPG
Teams: Portland Trail Blazers
There's not much to say about Greg Oden other than he was arguably the most hyped big man to come out in the draft since Kevin Garnett. Oden was the top high school prospect going into his freshman year at Ohio State and kept up the stellar play as he became a one-and-done player drafted first overall by the Portland Trail Blazers ahead of Kevin Durant. He has played a grand total of 82 games since he was drafted in '08 and despite flashes of some real ability, he will forever be in the "what if?" pile of players taken with the first pick. *cues the soundtrack* #hadtodoit #waytoocold
24. LaPhonso Ellis
Career years: 1992-2003
Career stats: 11.9 PPG 6.5 RPG 1.6 APG SPG BPG
Teams: Denver Nuggets, Atlanta Hawks, Minnesota Timberwolves, Miami Heat
Laphonso Ellis isn't the most known guy on this list, but his game and potential may rival some of the most famous players in the league. He was drafted No. 5 overall out of Notre Dame by the Nuggets and started off his NBA career strong with two solid seasons that made experts feel like he would be a premier power forward in the game going into his third season.
Just like the stories of many others on this list though, a stress fracture to his right knee kept him off the court for nearly his entire third season. That injury paired with more to his other knee and a sports hernia plagued Ellis for the rest of his career, never fully allowing him to live up to the hype. Remember he actually did this.
23. Jay Williams
Career years: 2002-2006
Career stats: 9.5 PPG 2.6 RPG 4.7 APG 1.1 SPG BPG
Teams: Chicago Bulls
Many forget just how highly touted and supremely talented Jay Williams was before his tragic career-altering motorcycle accident in 2003. He won the Naismith award in 2002 after an NCAA title run in 2001, and left the school with an average of 19.3 PPG, 6.0 APG, and 3.7 RPG from the point guard spot. He was so good, the Bulls drafted him No. 2 overall in 2002 behind Yao Ming. His rookie season wasn't spectacular, but he showed flashes of potential greatness, and quite possibly could've been their franchise guy.
22. Allan Houston
Career years: 1993-2005
Career stats: 17.3 PPG 2.9 RPG 2.4 APG SPG BPG
Teams: Detroit Pistons, New York Knicks
(All Knicks fans scream "Yes, son!" upon seeing this page). Allan Houston, the $100 million dollar man after being a year or two past his prime. He had some good years for the Knickerbockers, most notably the '99 Finals run where he made "The Runner" to beat Miami and land the No. 8 seed vs. No. 1 seed upset. Then the pesky knee injuries caught him in '03 and he only managed 70 games in the two years after until his retirement. There's no doubt he could have gone down as a Knick great if he was able to get a couple more productive years out of those legs. Melo, take notes.

... said:21. Jermaine O'Neal
Career years: 1996-present
Career stats: 13.4 PPG 7.3 RPG 1.4 APG SPG 1.8 BPG
Teams: Portland Trail Blazers, Indiana Pacers, Toronto Raptors, Miami Heat, Boston Celtics, Phoenix Suns
Jermaine O'Neal was part of the freshman class of today's prototypical star big man. He could dunk on you, he could step outside and hit a 15 footer, he could get at you on the defensive end, he was a worthy All-Star power forward on a stacked Pacers squad. That was until the rumble at the Palace and a slew of injuries to his shoulders, knees, and ankles. He's still playing now but he's not nearly the player he was in his prime. He could have been a possible future Hall of Famer had he kept up his production and stayed healthy but now he'll go down in history as a journeyman big who had a few good years.
20. Gilbert Arenas
Career years: 2001-2012
Career Stats: 20.7 PPG 3.9 RPG 5.3 APG 1.6 SPG BPG
Teams: Golden State Warriors, Washington Wizards, Orlando Magic, Memphis Grizzlies
You can hate on Gilbert Arenas all you want, but it's not debatable that Arenas was an offensive powerhouse when he was healthy and not bringing guns to practice. After some formative years in Golden State, Arenas signed with the Wizards and was on the verge of becoming a star from '04-'07, averaging nearly 28 PPG and six APG while leading Washington to the playoffs. At the tail end of the '07 season, however, he tore his MCL, and never played a full season again. Had he never gotten injured, the Wizards may have had a shot at being a serious title contender and Arenas may have been looked at now as one of the best scoring point guards of his era.
19. Jamal Mashburn
Career years: 1993-2003
Career stats: 19.1 PPG 5.4 RPG 4.0 APG 1.0 SPG BPG
Teams: Dallas Mavericks, Miami Heat, Charlotte/New Orleans Hornets
Monster Mash may own car dealerships, Papa Johns, and Outback Steakhouses today, but in his prime he got busy for Dallas and later the Hornets during his NBA career. A prolific scorer coming out the gate, Mashburn's career was forever tainted by multiple knee injuries. As one-third of the "Three J's" in Dallas (Jim Jackson and Jason Kidd) he had high expectations, but the three young stars had a hard time co-existing and they were eventually broken up.
After his time in Dallas, Mashburn managed to play more than 50 games in only three of the seven years he had left in the league. Although, he is one of five players to average 20 a game in his last season (Drazen Petrovic, Jerry West, Larry Bird, and Michael Jordan are the others).
Mashburn AKA Mosnter Mash, still my favorite Heat SF of all time even though Lebron is a far better player with all respect due to Lebron and Glenn Rice
... said:18. Fat Lever
Career years: 1982-1994
Career Stats: 13.9 PPG 6.0 RPG 6.2 APG 2.2 SPG BPG
Teams: Portland Trail Blazers, Denver Nuggets, Dallas Mavericks
Fat Lever has one of the most awesome names in all of sports, and also showed many that a point guard can rebound the ball and be a threat outside of dishing and shooting from the perimeter. Lever had a solid stretch from '86-'90 as a Denver Nugget averaging 18.9 PPG, 8.9 RPG, and 7.5 APG leading them to the playoffs every year. In 1990 Lever had a severe knee injury that held him out for most of the next two seasons and the entire '92-'93 season changing his NBA trajectory completely. Can we get back to talking about his name being Lafayette, though? 'Cause that's like amazing.
17. Danny Manning
Career years: 1988-2003
Career stats: 14.0 PPG 5.2 RPG 2.3 APG 1.1 SPG 0.9 BPG
Teams: Los Angeles Clippers, Atlanta Hawks, Phoenix Suns, Milwaukee Bucks, Utah Jazz, Dallas Mavericks, Detroit Pistons
When you're drafted No. 1 overall a ton of pressure is put on you to perform and be the face of a franchise. Danny Manning faced just that after being taken first by the L.A. Clippers. He suffered a torn ACL his rookie season that had him miss most of the year, and later had more knee surgeries to fix nagging injuries as he grew into a potential star in the league.
Despite managing a few good seasons from '92-'94, Manning never was able to play more than 20 games in one season for the rest of his nine years. Had he never had the injuries, many projected him to be a star in the league and a household name.
16. Brad Daugherty
Career years: 1986-1994
Career stats: 18.7 PPG 9.4 RPG 3.6 APG SPG BPG
Teams: Cleveland Cavaliers
Before LeBron James came around, Brad Daugherty held the title of greatest Cavalier ever as he proved prognosticators right after being the No. 1 pick in the 1986 draft. He was a legit center with real big man moves and a powerful tenacity that rivaled some of the games greats. Back injuries cut his career short however, as after eight seasons he called it quits already considered the franchise's greatest big man and All-Time scorer. Had he remained healthy who knows how he'd be remembered today, plenty of NBA fans probably don't even know who he was and he averaged almost 19 PPG and 10 RPG for his career! SMH
15. Ralph Sampson
Career years: 1983-1991
Career Stats: 15.4 PPG 8.8 RPG 2.3 APG 0.9 SPG 1.6 BPG
Teams: Houston Rockets, Golden State Warriors, Sacramento Kings, Washington Bullets
There aren't a lot of 7'4" guys walking around on Earth, let alone guys that size that can actually ball. Ralph Sampson was one of them. After dominating at Virginia, Sampson took his talents to the Rockets and started off his pro career strong averaging 20 and 10 with twi blocks to boot through his first three seasons. After the Rockets drafted Hakeem in 1985, they immediately became contenders, reaching the Finals in 1986. But Sampson eventually endured nagging knee and back problems which robbed him of his freakish athleticism.