Rivalries have always been a part of competitive sports. Some date back to the 1800s and continue through today.
But nearly every year, new hatreds emerge. Some prove to be short-lived circumstances-of-the-moment animosities, others take root and become long-standing grudges.
Click on to see some of the newest, fiercest rivalries in sports. Ponder. Wonder. Predict. Which are here to stay, and which will be gone by next season.
The Steelers and Ravens have battled for dominance of the AFC North in recent years, and it's gotten ugly.
While many rivalries seem are in the hearts of fans more than amongst players and coaches, this this one definitely permeates both the fields and the stands.
Steeler's James Harrison said last year, "I hate losing to [The Ravens]. I hate losing to anybody, but to them it's a lot worse."
The Astros have moved from the National League Central to the American League West.
But some other pretty powerful Rangers already have claimed that little piece of divisional turf, and in the words of the illustrious Marvin the Martian, "there just ain't room enough on this planet for the two of us."
The Astros and the Rangers get to show one another who the real sheriff in town is with an opening series beginning April 2, 2013.
We love sporting video games because you can do amazing stuff like pit Muhammad Ali against Manny Pacquiao. The 1989 San Francisco 49ers against the 1978 Pittsburgh Steelers. The 1966-67 Philadelphia 76ers against the 1995-96 Chicago Bulls. Rodger Federer against Rod Laver.
Well the UFC might just bring one of these greatest of all time bouts into the real world.
For years fans have daydreamed of a mega-fight between Anderson Silva, reigning middleweight champion and Georges St. Pierres, reigning welterweight champion. For fans of MMA, this would be epic. One for the history books. A clash of titans.
Now with the possibility of this fight actually happening, tensions are crackling.
The Lakers have been so dominant for so long, that many people may have forgotten that Los Angeles has a second NBA team.
Not so anymore.
The Clippers miserable existence (beginning as a team from sports-cursed Buffalo) may have ended, and their glory days finally begun.
Lots of chatter and debate going on now as to how the Clippers match up to their dominant big bro.
Let the Battle for LA begin!
The commish and his franchise owners have dug their heels in. With those locker rooms locked, millions of dollars in lost revenue have accumulated. In fact, every game missed is an estimated loss of $975,000 in ticket sales revenue to the league.
Fans hold on to a final hope for a short season beginning in January, but no one appears to be holding his or her breath.
While not so new, this rivalry has intensified greatly.
Now that the money and drug testing issues have been resolved for a potential bout between these two legends, the insults are flying.
Mayweather recently said that Pacquiao's acceptance of a less than fifty-percent share for a fight shows that he has become desperate.
Mayweather also jumped on Pacquiao's June 2012 loss to Timothy Bradley saying, "Once you take a loss and you're on the decline... Listen, Manny Pacquiao, whether he got cheated or not [against Bradley], his stock drops enormously after taking a loss. No matter how you took a loss, you took a loss."
Manhattan and Brooklyn have a long history of pooh-poohing each other. Manhattanites claim to be the elites of the Big Apple. Everyone else is just a wannabe from "the outer boroughs."
Brooklynites claim to be more real, less materialistic. More artistic. Better at hipsterism.
Well with two NBA teams now in town, the riff widens.
Adding to the territorial tensions is the fact the Knicks superstar Carmelo Anthony is a Brooklyn native "whom the Nets desperately tried to acquire to be the franchise centerpiece for their move."
With both teams playing well, this could be the start of a beautiful enemy-ship.
For years and years Notre Dame's many rivals (USC, Army, Navy, Purdue, Michigan State, University of Michigan, Stanford) got to chuckle and sneer as the once-powerhouse nested far down on the rankings list.
But The Fighting Irish have risen again, and they now sit perched on the highest branch, flexing their talons, eyeing their next prey.
On January 7, they will fight for the BCS Championship Title.
Brad Keselowski the young wonder-driver for Penske Racing is proving to be a thorn in the side for the mighty Hendrick Motorsports Racing Team, which is the most successful team in modern NASCAR history.
Among newcomer Keselowski's many recent triumphs is his winning of the Sprint Cup Series championship.
Fueling the rivalry is the fact that Keselowski once raced for the Hendrick Motorsports farm system. Consider him the one that the Hendrick empire let slip through their fingers, and boy is he letting them know it.
Grizzlies growled. Thunder claps resounded. These two teams have been crackling with mutual enmity.
But a November 2012 altercation between Memphis' Zach Randolph and Thunder's Kendrick Perkins have cemented the contract of hate which has no foreseeable expiration date.
With the Red Sox down in the dumps, the Yanks have turned their ire upon the Tigers.
No one in New York had forgotten the painful ALDS loss to the Tigers in 2006.
But the grudge may not truly have been put into place until the Tigers knocked out the Yankees again in 2011.
The goddesses of fate can be fair, though. They arranged for a beauteous chance for redemption and revenge in 2012.
The Tigers and Yankees squared off in the AL Championship series. This time, a ticket to the World Series was on the line.
With the Tigers sweeping the series, New York can only smart and daydream of the day when they slay this most persistent of foes.
City and United have been rivals since they both came into existence, so in some ways this is nothing new. But for decades City was David to United's goliath. Only this David had no slingshot.
While over the past decades United became "the greatest team of the Premier League era," City foundered in mediocrity.
But then along came Sheikh Mansour, royalty from the United Arab Emirates. He bought Manchester City, infused insane amounts of money into the franchise, and turned the club into a powerhouse.
In 2012 Manchester City beat Manchester United and went up to win the Premier League title.
The rivalry between the two teams has now gone global.
The Celtics have had a few famous rivalries, most notably with the Lakers and the 76ers. But those are now paling in comparison with the newly-emerged rivalry with the Miami Heat.
Dwayne Wade and Ray Allen have their own issues with the Celtics, but King James really seems to despise them. Many a playoff hope had been dashed by the Celts. And then there's the longstanding grudge between James and Celtic's Paul Pierce.
Former Celtic's guard Ray Allen's July 2012 decision to leave the Celtics for the Heat has fanned the flames and inflamed the fans.