Training camp is fast approaching for the National Basketball Association, offering a big opportunity for the league's fringe hopefuls to make their mark. Get yourself noticed as a non-guaranteed contract player and you could nail down one of the 450 jobs that exist league-wide (30 teams, 15 roster spots apiece). Just last year, Jordan Clarkson turned heads for the Lakers and transformed himself into a key future cog for the club, while Hassan Whiteside broke through as an inside presence for the Miami Heat and even earned some Most Improved Player first-place votes.It's worth remembering, though, that not every player that sticks in the NBA after training camp is on a path towards stardom. There are players that hang on for just a cup of coffee and others who manage to endure their own poor play along the way to a surprisingly long career of mediocrity. In some cases, these players have been acquired through a high draft pick or signed to a lucrative contract, making their continued survival a product of the big investment placed on them. In other cases, they are very good at being large humans, which is a skill that can't be taught.Any basketball player who manages to make it through to the world's top basketball league merits a pretty significant level of respect, but just as there are all-time great NBA players, there are all-time bad ones. Rather than focusing on the short lifespan players, this list zeroes in on those who managed to continually detriment their own team while somehow finding continued employment. While points have been awarded for those who dramatically undid major expectations with inept play, this isn't simply a list of the biggest draft busts. After all, even 1998 No. 1 pick Michael Olowokandi nearly averaged a double-double over an entire NBA season.Without any further ado, here are the 20 worst players in NBA history. Feel free to enjoy this list and those on it, but please keep in mind that they are all still so much better than you at basketball.

15 Brian Scalabrine

Easily the most popular player on this list, Brian Scalabrine made his name as the enthusiastic, towel-waving, bench-warming white guy on a number of good teams. Scal even has a championship ring as a member of the 2008 Boston Celtics, albeit without playing a single playoff minute that year. To be sure, 11 seasons, one ring, $20 million in salary and at least three nicknames (White Mamba, Veal Scalabrine and The Ginger Ninja) is a pretty solid legacy for a guy with career averages of 3.1 points and 2.0 rebounds.

14 Elliot Williams

This sort of list tends to produce the type of obscure, little-known players that even ardent NBA fans may not clearly recall, so it's not entirely surprising if the name Elliot Williams doesn't ring a bell. Well, except for the part where the former first round pick is actually a current NBAer. The 26-year-old bounced around between Utah and New Orleans on 10-day contracts last season, his third as a pro, averaging just 2.8 points on 37.8% shooting across the two stops. Undeterred, the Charlotte Hornets signed Williams, a D-League standout and a veteran of over 100 NBA games, to a tryout contract for the upcoming season.

13 Oliver Miller

"The Big O" had long since been taken by all-time great Oscar Robertson when Oliver Miller entered the league in 1992, but it might have been a better fit for the 280-pound Miller. Indeed, the Arkansas Razorbacks star struggled with both his weight and his game over nine NBA seasons, ballooning up to a reported 375 pounds while still in his playing days. When his NBA career came to an end, he couldn't even crack it as a Harlem Globetrotter, being released by the team for showing "no appreciation for what it takes mentally and physically to be a Harlem Globetrotter."

12 Mark Madsen

Credit Mark "Mad Dog" Madsen for translating what marginal natural basketball skill he had into a productive nine-year career that even included titles with the Los Angeles Lakers in his first two seasons. But about that marginal skill... Madsen never averaged as many as four points or rebounds, despite playing over 450 games and even starting 70, not to mention appearing in 49 playoff games. Madsen's enduring legacy from his basketball career is probably the terrible dancing moves he showcased during the second of three straight Lakers' title celebrations, which tells you all you need to know about his game.

11 Anthony Bennett

Throughout the summer, reports emerged that Minnesota was looking into possible trade options for Anthony Bennett, but was finding no takers. While no NBA observer would be remotely surprised to hear that the Timberwolves are struggling to drum up interest for the underwhelming Bennett, it's still pretty jarring to have 29 NBA GMs shrug when offered a 22-year-old former No. 1 overall pick. But that's how big a fall it's been for 2013's top pick, who scored double digits in scoring just eight times last season despite averaging 15.7 minutes per game. There's still time for Bennett to turn it around, but it's hard to imagine a worse start to his NBA career.

10 Brian Cardinal

The classic blue collar player, Brian Cardinal's nickname of "The Custodian" pointed to his decidedly non-glamorous, gritty stamp on the NBA. After averaging no fewer than 10 points in any of his four years as a Purdue Boilermaker, Cardinal couldn't reach double digit scoring averages in any of his 12 NBA seasons, topping out at 9.6 points in 2003-04 with the Golden State Warriors. Beyond his pail-and-bucket style, he is probably best known for scoring an eye-popping six-year, $34.5 million contract from the Memphis Grizzlies, where he promptly saw his minutes and production cut in half.

9 Ricky Davis

Ricky Davis might be the anti-Brian Cardinal, a player who had plenty of NBA-calibre talent who simply didn't come anywhere close to realizing it. Sure, Davis realized his potential long enough to average 20.6 points during a career-best 2002-03 campaign with the Cleveland Cavaliers. However, it tells you all you need to know about his career that he counter-balanced 736 regular season contests with merely 11 playoff games, of which his team won just three. If nothing else, Davis earned his place here for his dim-witted and selfish attempt to complete a triple-double by collecting a rebound off a miss on his own basket!

8 Nikoloz Tskitishvili

No one better exemplified the league's fascination with mysterious incoming overseas talent than Georgia's Nikoloz Tskitishvili, who was advertised as a seven-foot, athletic stretch four when he was selected fifth overall by the Nuggets in the 2002 Draft. Reports suggested that the Nuggets' front office had never actually seen him play and it's not as though his 6.6 points and 1.8 rebounds in 11 games with Benetton Treviso would have prompted a top-five pick. We will never really know what all the fuss is about, particularly in light of Tskitishvili's career average of 2.9 points per game.

7 Chris Jent

By some measures, Chris Jent can be considered one of the most successful players to ever set foot in the NBA. Consider his career in comparison to current NBA star Rudy Gay: Jent's NBA career spanned two years and included 37 total points, a plateau that Gay has exceeded four times over the course of a single game. And yet, Jent has 11 postseason appearances on his resume, compared to just seven appearances in nine NBA seasons for Gay. Remarkably, Jent played nearly twice as many playoff games as regular season games (six) in a highly forgettable career.

6 Keith Closs

Odds are, if you're 7'3" and athletic, you're going to get a shot in the NBA. And if you're Keith Closs, even a crippling, long-standing alcohol problem wasn't going to stand in the way of a three-year NBA career with the Los Angeles Clippers that included a five-year, $8.5 million contract with the team. Closs' unspectacular 130-game NBA imprint was made more notable by a checkered off-court history that included three DUIs and multiple clashes with Clippers coaches. Most notoriously, Closs was the subject of a viral video in which he is seen being beaten up by a mob of people.

5 Bryant "Big Country" Reeves

It proved to be a pretty bad omen for the long-term well-being of the Vancouver Grizzlies that the first player acquired in franchise history was Bryant "Big Country" Reeves, a seven-foot Oklahoma farm boy taken sixth overall in 1995. Reeves, who spent his entire six-year career with the Grizzlies, started off well enough to warrant a massive six-year, $65 million extension on his rookie contract. However, injuries and a stunning lack of mobility limited him severely. By the time the Grizzlies moved to Memphis, injuries and rapidly dwindling play were already cutting his career short. Who knows, if they had taken Damon Stoudamire instead, maybe Vancouver would still have a place on the NBA map.

4 Manute Bol

More a subject of public fascination than an actual basketball player, Manute Bol felt like something out of the reality show era. The 7'7" center from Sudan was all arms and legs when he came to the NBA as a second round draft pick of the Washington Bullets in 1985. While Bol's block totals were predictably impressive (five per game in his rookie year), he otherwise made the most basic of athletic movements look altogether impossible. An average of 3.9 points with the Golden State Warriors in 1988-89 would ultimately be a career-best for Bol, who would later go onto suit up for a hockey game in a public stunt.

3 Sun Yue

Left, 6'9" ball-handling two-guards don't come along every day, so the Los Angeles Lakers figured that it might be worth using a second round pick on Chinese import Sun Yue in the 2008 Draft. After looking somewhat competent in a short D-League stint, the Lakers offered Yue a platform to see what he could do for the purple and gold at the NBA level. It didn't go well. Following a debut in which he collected four fouls and two turnovers in five minutes, Yue would go on to accumulate more fouls (10) than points (six) and as many turnovers (three) as assists and steals combined. Ten games was all it took for the Lakers to realize that Yue simply wasn't an NBA player.

2 Cherokee Parks

Oh, to be the agent for the oddly named Cherokee Parks, who somehow leveraged respectable college numbers at Duke (12.5 points, 6.7 rebounds) into an NBA career spread across nine seasons and including seven teams. This, despite an offensive game that saw him top out at 6.3 points per contest and a defensive game that saw him consistently beaten in the post by faster, stronger and larger players. Since his game certainly didn't do the talking for him, Parks spent his pro career growing an impressive stash of tattoos all over his body, creating more of an eyesore than even his game ever could.

1 Javaris Crittenton

"Pick one" was allegedly the threat made to Javaris Crittenton by teammate Gilbert Arenas in the locker room of the Washington Wizards. The presence of guns in the locker room breached just about every player code the league had to offer and brought a swift end to Crittenton's non-descript NBA career. The 2007 first rounder made it to three different teams in two seasons before the Washington incident. In that time, he never cracked six points a game or 2.5 assists. He has since pleaded guilty to manslaughter and was sentenced to 23 years in prison.