After posting a 20-7 record in May, the Cardinals are 12-12 in June and suffered their first sweep at the hands of the Rangers last weekend. The A's have lost four of their last seven games and seven of their last 12, but appear to be on an upswing, winning both games of their two-game series with the Reds at O.co Coliseum.
As Oakland takes the field Friday for the series opener against the Cardinals, outfielder Yoenis Cespedes will continue slowly working his way back to form after a hamstring injury forced him to miss time earlier this month.
"I think it's more of a mental thing," said manager Bob Melvin. "He's not, maybe, 100 percent running down the line. It takes a little time. He's probably in the 90 percentile, where we're not worried about him reinjuring it at this point. We wouldn't have him in the outfield if we didn't think it was time to do that."
Entering Wednesday's contest, Cespedes was batting .156 in 11 games since returning from the injury on June 14.
"He's not happy about where his average is, but his production is still there," Melvin said. "He's always on the verge of a hot streak to me. He continues to do his thing and prepare and get better to where he's in the lineup every day."
Cespedes will have to contend with St. Louis rookie Shelby Miller, who is seventh in the National League in ERA at 2.35, just behind Cardinals ace Adam Wainwright (2.31), who will start against the A's on Saturday.
Miller will also be looking to get back on track Friday after surrendering a pair of two-run homers to the Rangers in his last start, a 4-2 loss.
Starting opposite Miller is Bartolo Colon, who will be pitching for his 11th victory of the season. The Cardinals' offense struggled against the Rangers last week but came alive in the first of two games with the Astros. The St. Louis batters won't have it easy against Colon, who is 7-0 with a 1.41 ERA and one home run allowed in 51 innings over his last seven starts.
"Against the Astros, we showed what we always do well: hitting with guys in scoring position, driving the ball and taking walks," Cardinals manager Mike Matheny said. "You're going to have tough weekends because there's very good pitching out there and good teams, but this isn't anything new. Our guys went out and proved that it's not something to worry about."
Cardinals: Matheny to use four-man rotation
With three off-days in nine days and no fifth starter, the Cardinals will go with a four-man rotation for the next two weeks -- until July 6, when Joe Kelly will start against Miami.
Miller, who last pitched Saturday, will start Friday against the A's, followed by Wainwright, Jake Westbrook and then Lance Lynn.
"Being the long guy out of the 'pen, my arm's ready to go for all situations," Kelly said. "When the off-days are over, I'll be ready then, too. It's ultimately the skipper and GM's decision, but it's exciting to have at least the opportunity."
Athletics: Crisp expected back in the lineup Friday
Center fielder Coco Crisp did not start Wednesday against the Reds to attend to a family matter.
"He's got a family issue he's dealing with right now," Melvin said. "Everything's fine."
Melvin noted that his pregame absence was not the result of an emergency but rather a "planned" event.
Chris Young started at center in Crisp's place and struck out in all four of his at-bats.
• Catcher Stephen Vogt, who made his A's debut Tuesday, went 0-for-3 but picked up an RBI on a sacrifice fly. Vogt went 0-for-3 again Wednesday and is still searching for his first big league hit after going 0-for-25 in three stints with the Rays last season.
• Tyler Lyons, who would have started Friday against the A's had he not been sent down to Triple-A last week, pitched seven scoreless innings against the Iowa Cubs on Tuesday, allowing just one hit.
Chad Thornburg is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.