By Bernie Miklasz

St. Louis Post-Dispatch

Cards’ rookie outfielder Oscar Taveras has cooled. It’s been a setback to his forward progress. Taveras heated up during a seven-game stretch that began when the team cleared a full-time spot for him by trading Allen Craig to Boston.

You can be disappointed by the lack of hard contact, and Taveras often seems out of balance when he swings. Moreover, you don’t think there’s any doubt that confidence is a factor.

What Tim McCarver and others have said is true: Taveras is having a brutal time with fastballs. According to STATS LLC he’s batting .197 against fastballs this season. And he’s seeing a lot of them, with fastballs accounting for 64 percent of the pitches thrown to Taveras.

Here are his batting averages based on fastball location:

High: .036

Low: .250

Inside: .200

Outside: .175

And pitchers aren’t trying to be cute; they’ve given Taveras a fastball the majority of their first pitches to him.

If anything Taveras needs to be more aggressive. Even though he’s getting a steady supply of first-pitch fastballs, Taveras has swung at the first pitch only 19.6 percent of the time. Only Matt Carpenter (7.9 pct.) has a lower first-pitch swing percentage among Cardinals’ regulars.

Another problem spot for Taveras: pitches high in the zone (or high out of the zone). His batting average on high pitches is .077.

Before we start shrieking that the sky is falling because of Taveras’ struggles with the fastball - as if this is the fundamental flaw that will doom him forever - it’s helpful to look at rookie Kolten Wong. Last season Wong batted .163 against fastballs. This season he’s 100 points better vs. fastballs, at .263, and that average continues to climb. In 2012, playing in the majors for the first time, Matt Adams batted only .178 against fastballs. Adams has hit over .300 against fastballs ever since. Again: patience.

Can hitting coaches John Mabry and David Bell do something to help Taveras? The rookie is responsible for his own performance, and has to show that he can be a good student and learn to make adjustments. But you’d also have to think that the coaches can assist Taveras in speeding up the learning curve.

You can be pessimistic, however. Simple reason: More than a few Cardinals hitters have needed fixing this season. How many have gotten better? How many have gotten worse? We still see too much of the same old thing. Ground ball … ground ball … ground ball … ground ball. You would like to be wrong about this and give Mabry and Bell props for their work with Taveras.

Cardinals manager Mike Matheny dropped Taveras to eighth in the lineup recently. Now you have to wonder what’s next. Will Matheny change the mix on occasion, and start using an outfield of Matt Holliday, Peter Bourjos and Jon Jay? Jay has been among the team’s most consistent hitters, and Bourjos can be counted on to provide the attributes of defense and speed.

In September, the Cardinals figure to call up one or more outfielders, with the candidates being Tommy Pham, Stephen Piscotty and Randal Grichuk. Don’t think Taveras will get buried but he could start to see fewer at-bats.

It’s a waiting game.

Waiting to see how long it will take Taveras to adapt and handle major-league fastballs.