You often hear stories of clubhouse cancers that exist in any sport, those whose selfish, destructive and often ego-driven outsized personalities make them a challenge to handle in the close confines of a team's locker room setting. Typically, however, the team has the good sense to limit this person's influence to the best of their abilities, offering limited locker room sway and trying to control the extent to which that player rubs off on his or her teammates. There's an axiom that suggests that having one headcase isn't a problem in the locker room so long you don't have two.

This only applies, though, if the player in question does, in fact, carry a limited role within the club's hierarchy. When the source of the problem also happens to be one of the most prominent voices on the team - or, even worse, one of the coaches - things can get particularly messy. An athlete who has been placed in a position of authority within their team dynamic has earned that role, ostensibly, because they have garnered respect among their peers for the professional manner in which they carry themselves. This can also tend to leave them subject to higher expectations than those that their teammates face, leaving the whole group vulnerable to a lack of direction if those expectations aren't met.

Every sport has its own version of a leadership role for those both on and off the field of play, whether it is clearly defined (the "C" on a hockey captain's jersey, for instance) or more tacitly understood (in the NBA, a club's identity often comes from its best player). On this list, you will see leaders across all sports and eras who have failed due to inaction, erroneous and often arrogant leadership and even some blatant abuses of power.

Here are the 20 worst leaders in sports history:

21 20. Tony Romo

Poor Tony Romo has taken a lot of flak during his career, with only some of it being warranted. The 35-year-old is actually a pretty great story, having gone undrafted and working his way up to the starting QB job in Dallas before cementing his arrival with a standout performance in his first start for the Cowboys, which came live on NBC Sunday Night Football. Romo has had a great career in the years since, but this is the NFL and he happens to play on America's Team. A 2-4 playoff record and a disappointing track record of coming up short in big games will be, fairly or unfairly, his legacy unless he can win the big one.

20 19. DeMarcus Cousins

It can be a tricky situation when a team's best player also happens to be its most erratic personality. DeMarcus Cousins is an absolute beast for the Sacramento Kings as a double-double machine and fearsome inside presence, but he's also hot-headed, moody and often immature. The Kings hope that the addition of veteran point guard Rajon Rondo along with the experience of returning small forward Rudy Gay can ease some of the focus on Cousins and take some pressure off the 25-year-old. In the meantime, though, rival GMs will surely be eyeing Sacramento to see if they finally get tired of his antics and put him on the market.

19 18. Shayne Corson

Shayne Corson had already put together a litany of transgressions during his NHL career, including dirty on-ice hits and bar fights off the ice, when he was named captain of the Edmonton Oilers before the 1995-96 season. As captain, Corson still put himself first, lobbying officials for an extra assist that he felt he was due and experiencing on-ice meltdowns after losses. After nearly coming to blows with rising star and would-be protege Jason Arnott, head coach George Burnett undid his earlier mistake by stripping Corson of the captaincy after just 34 games.

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17 17. Carmelo Anthony

When Carmelo Anthony arrived in New York to much fanfare after a trade from Denver in 2011, he was ready to embrace the spotlight and be "The Man." Four-plus seasons and just one playoff series win later, 'Melo has become known better for his ball-hogging play, moping and questionable injuries. The Knicks have tried to build around the scoring small forward with big-money players like Amar'e Stoudemire, Tyson Chandler and Andrea Bargnani, but each has turned into a disaster for what is quickly becoming a laughingstock franchise under owner Jim Dolan.

16 16. Ben Roethlisberger

In an era where we are rightfully mindful of issues of sexual abuse and harassment, it's pretty shocking to see how quickly and quietly the story about Ben Roethlisberger's alleged sexual assault of a Harrah's Lake Tahoe casino host went away. The allegations, which were settled in 2012, brought to light a regular trend of boorish, entitled behavior from the Pittsburgh Steelers QB that were chronicled in an eye-opening 2010 Sports Illustrated article. Even though the story has mostly gone away as Big Ben has continued his NFL career, it's hard to believe the respected Steelers organization still have him as the face of their franchise.

15 15. Norv Turner

Most failed coaches are hired to a role, fizzle out and then are only heard from again in decidedly less influential positions. What's most perplexing about Norv Turner is how many chances he's gotten despite showing that, well, he isn't very good at coaching professional football. The former Washington Redskins, Oakland Raiders and San Diego Chargers head coach owns a .483 winning percentage across 237 games, making him the NFL's most experienced coach to have lost more than he's won. Turner continues to lurk as the offensive coordinator for the Minnesota Vikings.

14 14. Luis Suarez

There is no question that star striker Luis Suarez is talented, but talent alone doesn't make you a leader, so it was surprising when Liverpool manager Brendan Rogers handed the Uruguayan the captain's armband last year in place of injured Steven Gerrard. This was a player, after all, who has incurred three incidents of allegedly biting an opposing player (one hadn't happened at the time of the anointment, mind you), one incident of racial abuse towards Man U's Patrice Evra and has even made obscene gestures towards fans. Suarez has since signed with Barcelona, where he isn't likely to sniff (or taste) the captaincy any time soon.

13 13. Kobe Bryant

No one can question the competitive drive of Kobe Bryant, who is a proven winner with five NBA championships and two Finals MVP trophies on his mantle. As a leader, though, the Black Mamba has left plenty to be desired throughout his career. Where other all-time great champions like Bill Russell and Tim Duncan have led by preaching a selfless, team-oriented style of basketball, Bryant has always boasted a sneering, domineering and selfish brand of basketball. The Lakers star has called out teammates repeatedly, been involved in very public clashes and has never met a shot he didn't like.

12 12. John Tomic

In most sports, becoming a coach means working your way up through the ranks and ultimately impressing enough people to earn a coveted spot. In tennis, players can pick whomever they wish as coach, which is when family normally gets involved. Young Aussie star Bernard Tomic is still coached by his father, John, who has continued in the not-so-proud tradition of crazy tennis parents by allegedly punching his son, headbutting Bernard's hitting partner and even being banned from ATP tournaments for a year.

11 11. Dion Phaneuf

The Toronto Maple Leafs haven't won a Stanley Cup since 1967, but still boast a long, proud history, so it was no small matter when they anointed Dion Phaneuf as the 18th captain in franchise history in 2010, succeeding the popular Mats Sundin. Five years later, Phaneuf hasn't exactly earned the same reverence as the Swedish legend. The tough, physical defenceman has struggled under the spotlight in Toronto, making costly defensive miscues and coming off as uncomfortable and largely unlikable in the press. It doesn't help that the club has gone 166-168-42 since Phaneuf assumed the captaincy, with just one playoff round in that time.

10 10. Richie Incognito

Guard Richie Incognito was part of the Miami Dolphins' six-player "leadership council" when he became embroiled in a nasty bullying scandal in 2013. Incognito reportedly led a brutal, on-going campaign of mistreatment that centered on young teammate Jonathan Martin alongside fellow leadership council member Mike Pouncey. According to an investigator's report, Incognito had subjected Martin to ongoing harassment that was often racial and deeply personal in nature. He was later suspended and ultimately left the team. He now plays for the rival Buffalo Bills.

9 9. Reggie Jackson

You simply can't argue that Reggie Jackson was a clutch slugger with the New York Yankees, given that his nickname was "Mr. October." Jackson's failures as a leader stem from his outspoken brashness and an out-sized ego that caused numerous conflicts with teammates and coaches, most notably with manager Billy Martin. Jackson, who once reportedly identified himself as "the straw that stirs the drink" with the Yankees, would frequently take complaints over Martin's head and directly to owner George Steinbrenner. The two, who actually won a World Series together in 1977, also nearly came to blows in the dugout during a nationally televised game at Fenway Park.

8 8. Allen Iverson

The press conference that Allen Iverson engineered in which he bewilderingly repeated the phrase "we talking about practice" 22 times has become the stuff of viral internet legend. It also highlighted his troubles as a face of the franchise player during his NBA heyday. Iverson was one of the league's biggest stars during the late-90s / early-2000s, but wasn't exactly a role model. His lackadaisical attitude about practice was trumped only by his selfish on-court play. Sadly, since retiring in 2013, Iverson has reportedly struggled with alcohol and gambling issues which were also evident during his playing days.

7 7. Joe Paterno

I am certainly not looking to speak ill of the deceased, but Joe Paterno's legend took a significant hit over the last year of his life. The once-beloved Penn State Nittany Lions head coach was fired in 2011 after 45 years at the helm after news of Jerry Sandusky's child sex abuse scandal came to light, revealing that Paterno had known of Sandusky's indiscretions and done little in response. The Penn State board ruled that Paterno had demonstrated "a failure of leadership" in the matter, refusing his offer to step down after the season and instead firing him immediately. He died from lung cancer complications two months later.

6 6. Ryan Leaf

There may be no bigger draft bust in NFL history than Ryan Leaf, the cannon-armed quarterback who was selected No. 2 overall out of Washington State University by the San Diego Chargers in 1998. Leaf's smug, hot-headed attitude landed him in fights with fans, media and coaches alike. He was even caught on camera telling a reporter, "Just F-ing don't talk to me, alright! Knock it off!" When asked about the poor play that defined his disappointing career, he would often shift the blame to teammates who he felt didn't do their part. Classy.

5 5. Roger Goodell

As far as leaders go, they don't get much more powerful than the NFL Commissioner. Roger Goodell has managed to maintain his place atop the NFL mountain despite a litany of questionable decisions and inaction that has plagued his tenure. Goodell has overseen an endless stream of PR disasters, including player safety, concussion lawsuits, rampant spousal abuse, a bullying scandal and, most recently, DeflateGate. Those watching his handling of the brutal Ray Rice abuse situation saw a man who appeared more concerned with protecting the image of the league than doing what was just and right.

4 4. Ben Chapman

Although the name may not be immediately familiar, you may remember Ben Chapman as the racist manager depicted in the 2013 film, 42. Although Chapman was a pretty good ballplayer as part of the dominant Ruth-Gehrig Yankee squads, he cemented his reputation with some savage heckling of Jackie Robinson as manager of the Philadelphia Phillies. While ethnic slurs were common in baseball banter back then, Chapman was apparently in a league of his own with harsh, vile taunting.

3 3. Bobby Petrino

If, as they say, nice guys finish last, it only stands to reason that jerks win. So it should come as no surprise that Bobby Petrino continues to find employment on account of his penchant for winning. However, that winning takes a backseat to a long list of transgressions, including jilting Louisville for the NFL one year into a 10-year contract and then leaving Atlanta for Arkansas partway through the season with just a note left for players as an explanation. Petrino's worst incident, however, was a 2012 motorcycle crash where he was found to be riding with a 25-year-old football assistant with whom he had been having an affair.

2 2. Greg Winslow

One of the lesser known names on this list, Greg Winslow was the swimming coach at the University of Utah when widespread sexual abuse allegations came to light in 2010. Winslow allegedly abused an under-aged female swimmer over a two-year period starting in 2005. The allegations unearthed a clear pattern of disgusting behavior from Winslow that included past incidents of sexual and physical abuse, with one former swimmer calling him "a manipulator and a monster." Winslow has since been fired from the university and placed on USA Swimming's banned for life list.