The rivalry between the St. Louis Cardinals and Cincinnati Reds is not as highly talked about as some of the others on this list.
But during the heat of this feud, things got rather ugly in the NL Central. There have been several on, and off, the field instances that have fueled this fire.
In '09, then Cardinals pitching coach Dave Duncan accused Reds' right-hander Bronson Arroyo of doctoring baseballs with pine tar. Cardinals' ace Chris Carpenter, along with John Smoltz (who pitched for the Cardinals briefly towards the end of 2009), accused the Reds of rubbing down baseballs improperly for St. Louis, giving them a batch that had a poorer grip.
But that was just the start.
In 2010, during a pregame interview, Reds' second baseman Brandon Phillips had some less-than-flattering things to say about his St. Louis opponents.
The very next night, with the Reds hosting the Cardinals, Phillips stepped up to the plate in the bottom of the first. Phillips, an outspoken but quirky ballplayer, offered his customary tap of the shin guards with his bat to catcher Yadier Molina (and the home plate umpire).
After hearing Phillips' comments from a day earlier, Molina wanted no part of the All-Star second baseman's "friendliness" and kicked the bat away. The catcher stood up and the two got into a shoving match.
Then, things got really ugly.
The benches and bullpens emptied, and the area behind home plate became a sea of red. During the fracas, Reds pitcher Johnny Cueto's cleat connected with the face of Cardinals' back-up catcher Jason LaRue, resulting in a nasty gash over his left eye and a slight concussion.
Once the dust settled, the managers (Tony LaRussa and Dusty Baker) were the only two ejected from the game. Ever since this battle royale, there has been a bitter taste in the mouths of fans from both sides. Publicly, the two teams have let bygones be bygones and have moved on.
But fans still boo Phillips in St. Louis and Molina in Cincinnati.
With both teams evenly matched and pitted in an annual battle for the top of the NL Central, who knows what else this rivalry has in store.
Current all-time record (from 1901 through 4/7/13): Cardinals, 1,078-946-16