MILWAUKEE -- Luke Weaver was breezing. He had faced the minimum number of batters, eight up and eight down. He had struck out five of them.

Then he hit some turbulence, and as often happens to young players in the major leagues, he couldn't pull up quickly enough. After getting ahead of the opposing pitcher, Milwaukee's Matt Garza, with one ball and two strikes, Weaver couldn't get the final strike. He walked Garza, and that sparked a brush fire he couldn't contain.

Jonathan Villar sliced a double to left field. Weaver threw another ball to Kirk Nieuwenhuis, which put him in a tenuous situation.

On the next pitch, catcher Yadier Molina set up well outside and even hopped another several inches wide of the target. But Weaver missed badly. His 81 mph changeup drifted over the inside part of the plate, and the big, left-handed outfielder didn't miss it. Nieuwenhuis pummeled the ball deep into the right-center-field stands to give the Brewers a 3-0 lead.

"I definitely could have taken a moment and stepped back," Luke Weaver said of letting the game get away from him in the third inning. Stacy Revere/Getty Images

That sequence in the third inning of the St. Louis Cardinals' 3-1 loss to the Milwaukee Brewers illustrates the difficulty of what Weaver is trying to do in his first few weeks in the major leagues. It highlights the perils of what the Cardinals are trying to do in trusting two newly promoted rookie starting pitchers in the final month of their postseason push.

"The hardest thing when you first get here is just to slow the game down," Cardinals veteran Jaime Garcia said before the game.

Weaver (1-2) said he lost his feel in the midst of the Garza at-bat and didn't argue with the notion that the game began to speed up on him for a few minutes. He got it back, admirably, but by then the damage was done. The major leagues are merciless.

"I definitely could have taken a moment and stepped back," Weaver said. "I think I definitely was a little angry with myself that that got away from me. That's the pitcher. You've got to just throw it middle-middle there. Then, those other pitches, the conviction just wasn't there."

Weaver and fellow rookie Alex Reyes, who will make his second career major league start Friday in Cincinnati, are getting their first taste of the majors at a time when the Cardinals can't afford developmental hiccups. The team is scrambling to reach the postseason for the sixth straight season and clinging to a 1 1/2-game lead for the second wild card.

But the team has little choice. Michael Wacha is out for the season because of a right shoulder injury. Veteran Mike Leake is out for at least another 10 days and probably more with a painful case of shingles.

The Cardinals are confident that these two rookie pitchers will be productive major leaguers -- and hopefully soon. Weaver, 22, showed unusual poise for a pitcher his age by getting out of a bases-loaded, one-out jam in the sixth inning. He got slugger Chris Carter to pop up and then struck out Keon Broxton.

Overall, Weaver pitched well, striking out 10 batters and allowing four hits in six innings. It was his second straight quality start.

He said he reached out to veteran Adam Wainwright after his outing to get advice on a midgame crisis like the one he faced.

"Sometimes, the mechanics, they get a little out of sync. The feel of the baseball, it comes and it goes," Weaver said. "It's about, in that moment, getting over the hump and really adjusting. It came just a little too late. I think that next inning, I got back into the groove, and the inning after that, I settled in. But those little moments right there, they take advantage of and can win them the ballgame."

There are advantages to using rookies, particularly when they are as talented as Weaver and Reyes. Opposing teams have far less information to exploit than they would with a veteran pitcher, and almost every time either pitcher takes the mound, he will be facing a lineup that has never seen him. That is a crucial edge.

Asked about trusting such inexperienced pitchers with two-fifths of his rotation, Cardinals manager Mike Matheny said he had zero hesitation to put them out there, now or in the postseason. Zero, he repeated.

"Right now, it's all about who looks right. Every start Luke's had, he's looked right to me. Everything I watch Alex do looks impressive to me," Matheny said. "I'm not going to hold them back just because of their lack of experience or their age. They keep showing us what they can do."

The two young pitchers also have resources beyond Matheny and pitching coach Derek Lilliquist. Under Wainwright's leadership, all the Cardinal starters watch one another's bullpen sessions. Just as Kyle Lohse provided veteran guidance when Garcia arrived in the big leagues and Chris Carpenter ran the show when Garcia and Wainwright arrived, it's up to Garcia and Wainwright to help Reyes and Weaver slow things down.

Here's how Garcia summed up his advice: "These guys are very good prospects. They're very good at what they do, and there's a reason why they came up here: because the team believes they can do the same thing. We have one of the best catchers in the game. Try to trust that, and keep it simple. As you gain more experience, you should be able to learn yourself and start making adjustments. Right now, just trust your catcher and trust your stuff."

Garcia said he is leery of overloading the two young pitchers, so he generally waits for them to approach him for pointers. The fact that Weaver immediately sought Wainwright's advice bodes well for the Cardinals' ability to continue their long line of outstanding pitching. In this case, the learning curve will need to be a bit accelerated.