"This time of year is so special for baseball," Eckstein said. "This is when the game is at its purest -- when you show up at the park, and the only thing that matters is whether you win or lose."
But his purest and most important contribution to a team is still to come.
The postseason legend told MLB.com on Friday that he probably will be donating one of his kidneys "within the next two years" to his sister, Susan Eckstein Gaines. Four of Eckstein's immediate family members already have received kidney donations. Eckstein was in New York for the National Kidney Foundation's annual New York City Walk on Sunday, in his role as NKF national spokesperson.
Eckstein thought he would need to donate a kidney in 2010 for his brother Kenny, but he discovered that his B+ blood type was not a match. His brother Rick -- the hitting coach for the same Nationals team that is playing Eckstein's former Cardinals club Friday night in Game 5 of the National League Division Series -- wound up donating to Kenny then. For Susan, David will be the right match.
"Everyone's doing well right now," David said at the MLB Fan Cave, where he came by as part of MLB's "Legends are Born in October" ad campaign. "... Rick gave one to my brother Kenny back in 2010, and everything's going well. My father's doing well. My one sister Christine is doing well. The next concern for us is actually my sister Susan. She's in stage four of kidney failure, which [means] probably within the next two years, she'll be looking for a kidney.
"Very fortunate enough, it'll be my turn. We actually have the same blood type, and usually if you have the same blood type and you're a family member, you should be a match. Once she goes beyond that 20-percent functioning of the kidney, we'll start doing the tests, and hopefully I will be that match, and I'll be able to give to her."
David is 37, and Susan is 42. The former said he has anticipated this all along.
"Definitely. Because not only is it within my immediate family, but right now at least four of the six kids -- if not five of the six -- have the problem, they have the disease," Eckstein said. "So at some time in their life, it looks like they're going to have to have a kidney transplant. But with modern technology, hopefully we'll be able to prolong it long enough.
"I had the opportunity to marry a wonderful woman in my life, Ashley, and she knows that was part of the deal when she stepped into the family, that she might have to step up and also have to donate."
Eckstein said about 7,000 walkers are expected to join him Sunday in Manhattan to raise funds and awareness. It is the largest of 95 such NFK walks year-round.
"The biggest thing about the National Kidney Foundation is just getting awareness about kidneys, because many people fail to realize the importance of what a kidney does," Eckstein said. "The kidney actually acts as your purifier. It removes all the toxins in your blood, and it removes excess fluid and regulates your blood pressure."
Eckstein emphasized the importance of awareness for the disease, and said that it is something that has flown somewhat under the radar.
"There are about 26 million people out there who have kidney disease today," Eckstein said. "So I definitely encourage people to get them checked up, because you really don't realize it until it's too late. Right now, we have over 397,000 people on kidney dialysis [and] over 93,000 awaiting a transplant. One in three Americans is at risk right now just due to their high blood pressure, their family history, and diabetes.
"So for me personally -- and my family history of having four of my family members already received kidney transplants -- I just advised people, at your next checkup, get them checked out so you have an understanding before it's too late. If you find out about it early, you can do something about it before it's too late."
David said Rick was out of the hospital within 24 hours and "was in the gym three days after" donating his kidney.
Of course, David also was talking a lot of baseball on Friday. He said he plans to go to San Francisco to watch the Cardinals should they oust the Nationals. But family is family, so there was no way he would be rooting against Washington later that night.
"You're torn. You're watching it, and I knew this could be a possibility," Eckstein said. "But everyone knows my close bonds with my family, so definitely family comes first in this situation.
"I think this is gonna be one of those classic matchups. It's harder to hit in the postseason. Now you have two of the best in Gio [Gonzalez], who has a good chance of being the Cy Young [Award winner] in the NL, and Adam [Wainwright], who I had the opportunity to play behind. He rises to big-time situations, so I think it's going to come down to who makes the fewest mistakes and the ability to get that key hit."
Eckstein said he gets a kick out of seeing Carlos Beltran on the Cardinals, given the 2006 NL Championship Series.
"That's the one thing you keep seeing, that curveball [Wainwright] threw to him, when we were playing at Shea," David said. "I know he's hoping he's on the other side of things this year."
Eckstein said he has enjoyed watching rookie Pete Kozma step into his old position at a key time.
"At first, it was like a rotating door. They didn't know who they were going to play," Eckstein said. "The fact that [Kozma] stepped up and has played a solid shortstop -- that's first and foremost, to be able to go out and make the plays. And he has some sneaky pop in that bat. He gives you a really good at-bat. To lose a guy like [Rafael] Furcal and have someone people might not have known about step in and do the job on this big stage ... it's been fun to watch."
As for the infield-fly rule call at Atlanta in the Wild Card game, where Kozma drifted back and then peeled off as the ball dropped, Eckstein said he never encountered that in his career, and he questioned whether a third-base umpire would have made the same call as the left-field ump.
"If he makes the catch, no one cares," Eckstein said. "But when you kind of put yourself in that situation of a little bit of a miscommunication, which you really couldn't predict, it leads to what we saw.
"I've definitely gone out that far and waved my hands, especially on the shortstop side. I seriously doubt they would do it on the second-base side, because if the ball falls, the legitimacy of actually turning a double play, it's highly unlikely."
Eckstein also keeps busy by taking a political science class online, as he works toward completing the final seven credits needed for his University of Florida degree. He just took midterms and said they were hard, then he will take a "leisure" class to finish it.
"I asked if they could just take into account that I wrote an autobiography," Eckstein said with a laugh.
Ashley was appearing at the nearby Javits Center for New York Comic Con, in her role as owner of the "Her Universe" business. The Ecksteins have the rights to female science fiction apparel for such franchises as "Star Wars" and "Star Trek."
"I like how the fans of sci-fi and baseball will never admit how similar they are," Eckstein said. "If you go over to the Javits Center right now, you're going to see people painted, dressed up, and if you go over to Yankee Stadium tonight, you're going to see the same people painted, dressed up in their favorite player's jersey. So there are a lot of similarities."