And from the look of things, it's perhaps as bitter as ever.
Officially, the age-old rivalry was renewed for 2018 in the Red Sox's 14-1 thumping of the Yankees at Fenway Park on Tuesday. But unless you count how the home team put up all of its runs, there were no fireworks in that one. The two sides regarded each other with the same mutual respect that's been the standard in their matchups for over a decade.
Then came Wednesday's tilt.
The box score says the Yankees struck back with a 10-7 win, fueled by a pair of home runs by Gary Sanchez and five combined hits from fellow sluggers Aaron Judge and Giancarlo Stanton. The headlines, however, will be concerned with the heated exchange at the beginning and the brawl at the end.
The former took place in the top of the third inning, when Red Sox shortstop Brock Holt took exception to a hard slide into second base from Yankees first baseman Tyler Austin:
The benches emptied, but no punches were thrown and cooler heads prevailed.
But when Joe Kelly faced Austin in the top of the seventh inning and nailed him in the ribs with a 98 mph fastball, all bets were off. A bat was slammed, a challenge was issued and fisticuffs ensued:
Of course, there's no condoning any of this.
While Yankees manager Aaron Boone opined that Austin didn't do anything "remotely dirty," per MLB.com's Bryan Hoch, the way he went in with his spikes up and clipped Holt's right leg calls that into question. And given that Dustin Pedroia was lost to a similar slide in 2017, it's understandable if Austin's slide riled up the Red Sox.
Even still, resorting to throwing at hitters for revenge is the kind of thing that should have gone extinct years ago in Major League Baseball. It's a toxic tradition, and it's made all the more toxic when the agent in question is moving at damn near 100 mph.
Ultimately, what we have here is an Alonzo Mourning GIF situation. You can shake your head at the sheer dumbness of Wednesday's action, but you also can't help but nod optimistically about the larger meaning of it all.
For the first time in a long time, the Yankees-Red Sox rivalry feels like a rivalry again.
These two teams have been battling each other for close to 120 years. They've played literally thousands of games against each other, quite a few of which had enormous stakes.
For many years after that 2004 clash, however, there was relative peace.
That fateful 2004 season ended with the Red Sox dispatching the Yankees en route to their first World Series title in 86 years, thereby snapping the "Curse of the Bambino." The two teams subsequently underwent plenty of changes in the ensuing years. As a side effect, they weren't always contending at the same time.
But now, things are different. The fates have aligned in such a way for the rivalry to reignite.
Once Mariano Rivera (2013), Derek Jeter (2014) and Alex Rodriguez (2016) all moved on, the Yankees were largely free of ties to their great teams of the 1990s and 2000s. When David Ortiz hung up his own spikes after 2016, the Red Sox found themselves in the same boat.
In came the new guards, led by players like Judge, Sanchez and Luis Severino in New York and Mookie Betts, Chris Sale and Craig Kimbrel in Boston. With them came the promise of fresh faces putting a fresh spin on baseball's most notorious grudge.
Not so coincidentally, the games between the Yankees and Red Sox in 2017 started to count. Quite a lot, in fact.
Using a stat called "championship leverage index" as a measuring stick, FiveThirtyEight's Neil Paine concluded last September: "New York and Boston have played more meaningful contests in 2017 than they did in the previous seven seasons combined."
The season ended with both clubs in the playoffs for the first time since 2009. And while they didn't end up meeting in October for the first time since Boston's comeback from down 0-3 in the 2004 American League Championship Series, the stage was nonetheless set for an arms race like the ones that spurred on their early-2000s confrontations.
It didn't disappoint. The Yankees added Stanton, who was fresh off a 59-homer season with the Miami Marlins that won him the National League MVP. The Red Sox responded with J.D. Martinez, who hit home runs at an even better rate than Stanton in 2017.
After taking many years to deflate into nothing, it's hardly taken any time for the Red Sox-Yankees conflict to escalate back into something. Further escalation is almost guaranteed to follow.
If they can't play nice in their first two regular-season games, they aren't likely to do so over their next 17.
Stats courtesy of Baseball Reference.