With the A's and Giants set to renew their rivalry this week in San Francisco, we figured this would be the perfect time to rank the best players to play for both teams during their career.
Some of these players spent less than a full season with the A's or Giants, but if they donned the uniform for even one game, we're counting them.
So without further ado, here are our top 10 players to suit up for both the A's and Giants.
CLICK HERE FOR THE BEST 10 PLAYERS WHO JOINED THE A'S AND GIANTS
You couldn't have scripted it any better.
Mike Yastrzemski, playing his first game in his grandfather Carl's old stomping grounds in the series-opener between the Giants and Red Sox on Tuesday, did what his grandpa did so many times. He launched a home run over the wall at Fenway Park.
The special moment came in the top of the fourth inning, when Yastrzemski blasted a 3-1 fastball off of Boston starter Nathan Eovaldi 401 feet to dead center.
The younger Yastrzemski led off the game and received a standing ovation from the Red Sox crowd ahead of his first at-bat. He ended up striking out, but got the better of Eovaldi the next time around.
The home run increased Yastrzemski's season total to 20, giving the Giants two outfielders -- Kevin Pillar being the other -- with 20-or-more home runs for the first time since 2006 when Barry Bonds and Moises Alou accomplished the feat.
Perhaps most impressive of all, Yastrzemski's 20 homers have come in just 97 games with the Giants.
Not too shabby for a 29-year-old rookie.
Mike Yastrzemski knew his return to Boston would be a big deal for his family, but he also knew how much it would mean to Red Sox fans who grew up cheering for his grandfather, Carl. Those fans showed their appreciation Tuesday when Yastrzemski stepped to the plate to lead off for the Giants.
Yastrzemski got a nice ovation from the locals -- and a sizable Giants contingent -- before his first professional at-bat at Fenway Park. He grew up coming to games at the park and considered himself a diehard Red Sox fan.
Yastrzemski said before the game that he planned to take the moment in.
"It'll be cool. I don't get wrapped up in moments very easily," he said. "I've kind of trained my whole life to block out situations and crowd noises and stuff, but I think tonight I need to take a step back and get lost in one of the moments and appreciate that and experience it and then we can get back to playing baseball."
[RELATED: Yaz, family ready for emotional series at Fenway]
Yastrzemski went down swinging in his first at-bat, but it was still a successful inning for the Giants. As Yastrzemski was settling back into the dugout, Brandon Belt hit a solo shot over the Green Monster.