ST. LOUIS -- The Cardinals will be without their All-Star second baseman for an indefinite period of time after an MRI exam revealed that Matt Carpenter sustained a Grade 2 strain of his right oblique in Wednesday's 7-5 loss to the Pirates.

Carpenter was placed on the 15-day disabled list on Thursday and replaced on the roster by catcher Michael McKenry. The injury not only halts what was shaping up to be one of the best seasons in history by a leadoff hitter, but it will also keep Carpenter out of Tuesday's All-Star Game presented by MasterCard.

The oblique injury came one day after Carpenter was named to the National League squad. Teammate Aledmys Diaz was chosen to replace Carpenter on the roster.

"It's not how you design it, but things like this happen," Cardinals manager Mike Matheny said. "You have to make the most of it and take advantage of the rest that the rest of his body will get. And then plan on riding it hard after the rest."

A timeframe for Carpenter's absence is not yet known, though oblique injuries cannot be pushed. Something as seemingly innocuous as a sneeze or twisting of the torso can set back recovery time significantly. Carpenter missed one month with a right oblique strain in 2012.

"He's a tough player, and he's been given the sermon already that if you try to push this, it could last a lot longer," Matheny said. "And I gave him my story. I was able to play through a bunch of things people told me I couldn't play through. But [an oblique injury] was the one -- the first time I ever went on the DL in my life."

With Carpenter out, the Cardinals will have a void to fill at second base and in the lineup's leadoff spot. Kolten Wong drew the start at second on Thursday against the Pirates and could be positioned for regular playing time there again. Wong lost his starting job at the position last month when Carpenter shifted from third base to second base.

Greg Garcia and Jedd Gyorko are also fill-in options.

The leadoff spot will be even more fluid. Carpenter had batted first in 74 of the team's first 84 games and been a catalyst from that spot. At the time of his injury, Carpenter led the NL with a .420 on-base percentage and ranked second in the league with a .988 OPS. He was on pace to become the first leadoff hitter in Major League history with more than 100 RBIs in a season.

Matheny said he will choose who fills the top spot in the batting order based upon matchups and recent production.

"It's an opportunity for someone to step up and do something great and shine," Matheny said. "We're going to give guys opportunities, and they're going to have to make the most of it. It's going to be a great test for us."

Fantasy spin | Fred Zinkie (@FredZinkieMLB)

Hitting .298 with 14 homers, 53 RBIs and 56 runs across 351 plate appearances and eligible at three infield positions in most leagues, Carpenter will leave a major void in fantasy lineups during his extended absence. The Cardinals will likely use Kolten Wong at second base in the coming weeks, which may open up outfield playing time for slugger Randal Grichuk. Both players have value in deep-mixed leagues. Meanwhile, Carpenter owners looking for a replacement with multi-position eligibility should check the waiver wire for Javier Baez or Yangervis Solarte.