Jason Varitek and Alex Rodriguez were great sparring partners in that epic 2004 Red Sox-Yankees brawl

2004 was a wild year for the Yankees and Red Sox. Coming on the heels of a 2003 ALCS showdown wrought with tension, high-stakes heroics, brush-backs and bench-clearings and a now-iconic Aaron Boone walk-off in Game 7, the series was essentially a forecast of what was to come.
And while the real drama surfaced when the two clubs met in the '04 ALCS (you may remember how that played out), there was a sneak preview on a particularly action-packed afternoon at Fenway Park. On July 24, the two American League East rivals engaged in a slugfest ultimately won by Boston, 11-10 -- but this one was much more than a box score. 
In the sixth inning, Bronson Arroyo drilled Alex Rodriguez in the elbow with a pitch. A-Rod was not thrilled about this. Seconds later, everything happened: Rodriguez took some steps toward the mound until Boston catcher Jason Varitek put himself in his way. They exchanged shouts, and, soon, shoves: 

Both teams' rosters and bullpens then did the usual thing, skirmishing along the first-base line, each player and coach backing up a teammate or sparring with one from the other team.
Gabe Kapler was glaring: 

Tanyon Sturtze was bloodied: 

Speaking of sparring, the still image of Varitek and Rodriguez's tussle looks like a wrestling promo: 

It's hard to say just where this one lands on a list of the most iconic moments of the rivalry in the early 2000s, but it's up there.
Theirs was (and is) a rivalry of a special degree, and this all happened before Boston staged an unprecedented comeback a few months later after Dave Roberts stole second base, stunning the Yankees by turning an 0-3 ALCS deficit into a thrilling (or heartbreaking, depending on your perspective) Game 7 victory en route to their first World Series title since 1918.