Mike Petke once headbutted Jason Kreis, now they're New York derby coaching foes | SIDELINE

The New York derby will be chock full of fun and interesting storylines by the time it kicks off in 2015.

Not the least of which will have been bred right here in MLS during the playing careers of the two teams' coaches — Mike Petke, of the New York Red Bulls, and Jason Kreis, now of New York City FC — who maybe didn't always see eye-to-eye on things in their playing days.

Well, they did, literally, in the above GIF — even if only for a brief moment before Kreis hit the deck when Petke headbutted him as response to a Kreis hand to the face.

Following Petke's red card ejection in that game, his then-MetroStars went on to lose 2-1 to Kreis's then-Dallas Burn. Their lone regular-season meeting as head coaches ended in a very dramatic 4-3 Red Bulls victory this July.

For all the local rivalries around MLS, and for all the former MLS players now showing promise as head coaches throughout the league, the New York derby will be one of the first  between two teams each led by one of those men.

One final common "thread" among these young, up-and-coming, American coaches: great sideline fashion. Examples: Kreis vs. Petke.