It showed up when leadoff hitter Willie Bloomquist hit the first pitch he saw from Yovani Gallardo into center field, and again three pitches later when he stole second base.
The flip side of that aggressiveness also showed up in the second out of the game, one that turned out to be a key early turning point in the Brewers' 4-1 victory Saturday at Miller Park.
On a single to left by Justin Upton, Bloomquist didn't break stride as third-base coach Matt Williams waved him around third toward home. But Brewers left fielder Ryan Braun zipped a two-hop throw home to catcher Jonathan Lucroy, who put down the perfect block of the plate to keep Bloomquist from scoring the game's first run.
Anybody who has watched the D-backs' rise to postseason status this season knows there were no regrets in the Arizona clubhouse afterward.
"We're not going to change the way we play the game," Bloomquist said. "We're an aggressive team. We're going to make them throw us out. Hats off to him: He made a good throw.
"But if we get in that situation again tomorrow, chances are we're probably going to be running again."
And, if the crispness of the Braun-Lucroy connection is any indication, the Brewers have a good chance to turn the D-backs' aggressiveness into an out.
Braun, who did plenty of damage on the offensive side with a 3-for-4 day at the plate, created the defensive highlight of the game by turning what could have been a difficult play into a strikingly efficient one.
"It took a bad hop, he hit the ball pretty hard, so I improvised, relied on my athleticism and was still able to make a pretty good throw, and that was a great catch and block by our catcher," said Braun, who punctuated the play by spreading his arms in the "beast mode" sign to his teammates.
Added Lucroy: "For me as a catcher, I couldn't ask for a better throw. It was right there. I just tried to get in front of the plate and wear it if I had to. It was a good throw by him. He made a heck of a throw right there."
With it, the D-backs missed out on an early opportunity to get on the scoreboard against Gallardo, who made it clear from there that would be the D-backs' best chance of the day to piece together a run.
"Who knows? That run scores, it might be a whole different ballgame," said Gallardo, who allowed one run on four hits for the victory.
The Brewers couldn't have been surprised to see the D-backs being aggressive on the basepaths like that, particularly on the road in a playoff opener. The D-backs themselves probably would have been shocked if Williams had thrown up the stop sign, which would have put runners on the corners with one out.
Bloomquist would have been.
"With Matty there especially, I'm expecting to go all the time, just go until he stops me," said Bloomquist, who went 2-for-4 in his postseason debut after 845 games and 10 years in the Majors. "That's just our mentality that we have. Sometimes we're going to get caught, like today. Sometimes we're going to be safe and steal a run here and there."
It's pretty evident putting up a stop sign wasn't something that was on Williams' mind at all, unless perhaps Bloomquist had stumbled and fallen.
"That's the way we play," said Williams, a former All-Star at the hot corner. "It's a situation where Ryan made a nice throw, a nice two-hop throw to the plate. He stopped on the ball and used his arm strength to throw the ball to the plate and made a nice throw.
"But, hey, we're going to push it, and we're going to keep pushing it."
That has been the D-backs' mantra all season long. That stylized "A" on their logo might as well stand for aggressive.
Said Upton: "We were pushing the envelope in the first inning, but we had a lot of game to play with and we didn't get it done."
And whether it's the first inning or later come Sunday's Game 2, the D-backs figure to be pushing the envelope again.
"We've just got to keep after it and keep putting ourselves in those situations," Bloomquist said.
John Schlegel is a national reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.