But even more endearing is Costner's allegiance during this Fall Classic. He's a fan of the Tampa Bay Rays, a franchise that came into existence 10 years after "Bull Durham" was released and, quite frankly, wasn't competitive until the 20th anniversary of the movie that became an instant classic as soon as it hit the theaters.
But Costner is a proud Rays fan, even if he's somewhat new to the Tampa Bay scene. The friendship between the actor and the team began right around this time last year, when the Rays dropped the "Devil" from their name and overhauled their image, introducing a new logo, new uniforms and a new winning attitude.
They also introduced a new friend -- Costner, who was approached by Rays director of marketing and promotions Brian Killingsworth, and was asked if he'd be interested in helping usher in the new era with an appearance at the party.
Costner agreed, and he and his band, Modern West, performed nearly two dozen songs in front of approximately 10,000 fans at Straub Park for an evening Rays principal owner Stuart Sternberg described as an "11, on a scale of one to 10."
For Costner, an Oscar winner who in addition to "Bull Durham" starred in baseball hit movies "Field of Dreams" and "For Love of the Game," the event was an easy sell.
"Brian called me, knowing I have an affinity for baseball," he said via cell phone from California. "He said, 'Would you come down here and play? We're trying to turn this thing around. We're unveiling a new uniform, a new look for Tampa Bay.' I like a party as much as the next person and [the Rays] bent over backward for us. They made it easy."
After the event, Costner went back to California and kept in only casual touch with his contacts at the Rays. But they reconnected late in the season after the Rays endured a gut-wrenching loss after a walk-off grand slam by Blue Jays catcher Gregg Zaun, which sent the Rays to their fourth loss in five games.
Costner was also in Toronto, tending to other business, and he eventually met up with Rays manager Joe Maddon.
"I got to talking with Joe, talking about where they're at," Costner said. "I was trying to find some kind of mojo for everybody. I told him they needed a war song."
So Costner wrote a song titled, "It's All Up to You" and dedicated it to the Rays. The chorus relayed an encouraging message: "You've got to swing for the fence/Give a hundred percent/Dust yourself off, get up and do it again/You're the only one that can make your dreams come true/You're the only one, it's all up to you."
"It wasn't really for the public," Costner said. "It was for Joe and for the locker room. I wanted something to be their's. I sent it to Joe because there's a lot of pressure. I don't know if they play it or not, but it's nice to come into a locker room and have something that's their's."
Costner, who also has an allegiance to the Dodgers and Yankees, hasn't attended any postseason games in person, but he's been watching the Rays on television. He suffered through Game 5, when they sacrificed a seven-run lead to the Red Sox and lost by a run, and he celebrated when they finally clinched after a tight Game 7.
"I remember watching [Game 5], and they expanded the lead five, then to six, then to seven and my friend said, 'Let's go have dinner,'" Costner said. "I said, 'I don't feel good about this. I've been watching them all year. I'm not going to walk away from this now.' I thought it was an incredible game. That's the magic of baseball. Baseball doesn't care what you think. It doesn't care that you think the game's over in the seventh. To the nine guys on the other side, it's not."
Asked if he'd make it to St. Petersburg if Games 6 and 7 are necessary, Costner hedged a bit. He is, after all, a baseball nut, which by definition makes him superstitious by nature. He figures he'll keep his distance through the Series and then make a beeline to Tropicana should the team win it all.
The Rays have already asked him to play at their celebration, should they get that far.
"I might watch at home, and if they win, they'll have a party a day and a half later and I could come to that," Costner said. "But it's like they say in 'Bull Durham' -- never screw with a winning streak."
Alyson Footer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.