And now, Jacoby Ellsbury is the one transitioning from Boston, where he won two World Series championships, to the Bronx, where the Yankees are hoping the speedy center fielder can help them recapture that type of glory.
When the forever rivals open a four-game series Thursday night at Yankee Stadium, it will mark the first time Ellsbury plays against the Red Sox during his career.
The Red Sox selected Ellsbury in the 2005 First-Year Player Draft, and placed him in their leadoff spot from 2008-13.
Ellsbury is off to a hot start with his new team, although he went 0-for-4 on Wednesday against the Orioles after taking a .414 average into the game.
The Red Sox know full well what he is capable of.
"Obviously the biggest thing is keeping him off the base," said Red Sox manager John Farrell. "He can create a lot of havoc. It was fun to see him in your own uniform. As dynamic a player as he can be, he's going to benefit from the dimensions in that ballpark. But I think we've got a pretty clear understanding of where his strengths are and how we execute to that will be the key for us just trying to control him."
Clay Buchholz, Ellsbury's longtime teammate, will be Boston's first pitcher entrusted with keeping the leadoff man off the bases.
"He's just a high-caliber center fielder, high-caliber leadoff guy," said Red Sox outfielder Jonny Gomes. "It will be a little bit interesting for the core guys who have seen him in a Red Sox uniform their whole life. I think there's a lot more stories in between the lines than that one. It will be a good series."
Ellsbury had a chance to reunite with some of Boston's players before a Spring Training game in Tampa, Fla., but he didn't play that day because of an injury.
"I mean, you spend nine years with one organization, and you're drafted by them, went through the Minor League system and everything, it'll be different [to play against them] obviously," Ellsbury said in March. "But I'm definitely excited for the opportunity I have here. I'm definitely blessed to play in that organization. I won two championships. Those are the memories I'm going to have, all the positive stuff. But yeah, I feel very fortunate to be over here with these guys, it's a great organization. These guys are hungry, wanting to win."
This is the first of 19 meetings between the rivals this season.
Ellsbury will come to Fenway for the first time since the World Series parade on April 22, when the Yankees come in for a three-game series.
"I think it'll be interesting for him," said Yankees manager Joe Girardi. "My thought process is that it'll be a little bit more interesting when we go there. He'll have a lot more people that are happy that he's here than maybe when we go there."
Red Sox: Buchholz hopes to bounce back
Buchholz produced the exact opposite of what he was looking for in his 2014 debut, when the Brewers rocked him for 13 hits and six runs over 4 1/3 innings.
The right-hander and Farrell both were adamant that health didn't play a role in the subpar effort.
Buchholz hopes to redeem himself against the Yankees.
"I don't think you see true velocity built until you get into the month of May and see how they maintain it over the course of the entire outing," said Farrell. "Regardless of what a pitcher has, it still comes down to location."
Yankees: Pineda looks to build off first start
In Michael Pineda's first Major League start since 2011, he fared well, holding the Blue Jays to five hits and a run over six innings.
However, Pineda took a tough-luck loss and will try to reel in his first win for the Yankees on Thursday.
"I'm very happy about everything, because everything is doing good, and that's what I'm looking for," said Pineda after that start. "I've been working hard for the last two years to be here, and I'm happy with it."
- No Boston hitter has more than three career at-bats against Pineda.
- Red Sox outfielder Grady Sizemore, who is playing in the Majors for the first time since 2011, has two homers and five RBIs in 39 career at-bats at Yankee Stadium.
- Major League Baseball announced on Wednesday that a new award will be presented annually to each league's best reliever, with the American League award being named for legendary Yankees closer Mariano Rivera.
- Masahiro Tanaka fanned 10 in his Yankee Stadium debut on Wednesday night, though he came away with a no-decision.