Theirs is the heart of of a champion. Maybe that's the best way to say it. Sometimes, cliches are true.
The A's are young and resilient. They're also tough as nails. They're talented, too, way more talented than they're sometimes given credit for.
To focus on their 12 rookies or the eight players 25 or under is to miss the larger picture. They're expertly constructed, brilliantly managed.
They've also got a bunch of guys -- and age does not matter in this kind of thing -- who believe anything is possible.
"We're going to play every out," designated hitter Seth Smith said.
He spoke these words loudly, shouted them almost, in a clubhouse filled with music and laughter and confidence.
That attitude sounds like the simplest thing in the world, but it's one of the things that separates champions from those who only talk the talk.
On the other side of the room, third baseman Josh Donaldson was asked about that mentality.
"Success breeds confidence, and that's what happened the entire year," he said. "It's not just something that showed up today."
With their season down to its final three outs, the A's rallied for three runs off Detroit closer Jose Valverde and a 4-3 victory Wednesday night.
Now this best-of-five American League Division Series is tied at two games apiece, with Parker going against Tigers ace Justin Verlander on Thursday.
Verlander might be baseball's best big-game pitcher, so even after suffering a gut-twisting defeat, the Tigers know they have a safety net.
But the A's are feeling pretty good about things. After losing two in Detroit, they've come back to tie the series in front of big, noisy crowds at the Oakland Coliseum.
In two games, they've played terrific defense and gotten good pitching. And trailing 3-1 in the ninth on Wednesday, they found some magic.
"Is that the best game you've ever seen?" A's closer Grant Balfour asked.
Yep, it would make almost any list. When A's reliever Ryan Cook walked off the mound at the end of the top of the ninth inning, he began to scream the moment he reached the dugout.
"This ain't over!" he yelled.
And then he said it again.
Balfour went down the dugout challenging his teammates to envision a game-winning celebration.
"We're going to rock this guy's world!" he said of Valverde.
Later, he would say, "The mind is a powerful thing. It's an unbelievable win."
A's right fielder Josh Reddick led off with a single, Donaldson doubled and Smith drove them both in with a double to right-center.
"The amount of emotion going through me right there was uncontainable," Donaldson said.
Two hitters later, center fielder Coco Crisp ended it with a single to right, and the A's poured onto the field, just as they'd done after 14 walk-off victories during the regular season. They carried the celebration right into the clubhouse.
"You know what? We've done it too many times down this road to feel like we weren't going to win," A's manager Bob Melvin said. "And then we get the first guy on and we feel like here we go again. That's a contagious feeling in our dugout."
All the little pieces fit. Rookie A.J. Griffin allowed two runs in five-plus innings, and three relievers gave up one run in four innings.
The A's had extended at-bats enough to force Tigers starter Max Scherzer out of the game in the sixth inning. His departure meant manager Jim Leyland had to try to get 11 outs from baseball's 18th-best bullpen in terms of ERA.
"That's what we've been doing all year," Cook said. "It's not any one guy in particular. Someone steps up and makes up a play whether it be a diving catch or a big hit. We've just got to keep at that."
It was three hours, 21 minutes of tense playoff baseball, a game that tested both sides, a game that had a little bit of everything.
The Tigers were bitterly disappointed at not being able to wrap it up, but years from now, they may look back and feel proud they were part of something so special.
"That's why this is the greatest game of all," Leyland said.