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5/26/2013 5:30 P.M. ET

Gast placed on DL with left shoulder strain

LOS ANGELES -- John Gast became the fourth member of the Cardinals' pitching staff to land on the disabled list this month as the Cardinals moved him to the 15-day DL on Sunday, after Gast was diagnosed with a left shoulder strain.

The organization will have a better handle on the severity of the injury after Gast visits with team orthopedist Lyndon Gross on Tuesday. However, Gast's minimum two-week absence requires that Cardinals find another starter to plug into the rotation.

Gast described his left shoulder as "pretty sore" a day after he faced six batters in an abbreviated start against the Dodgers. The club has since learned that Gast had been dealing with shoulder soreness throughout this season, though he did not alert the Cardinals to any issues until manager Mike Matheny pressed him for an explanation as to why his velocity was down and his command off on Saturday.

In hindsight, that shoulder tightness may explain why it had been taking Gast longer than usual to get his arm loose while warming up in recent weeks.

"Every day since he got here, it's been, 'It takes me a while to get going. Once I get going, I'm fine,'" Matheny said. "So yesterday, I just thought that was an extension of that. I could finally get him to speak right before his at-bat [in the second inning] that he wasn't feeling right."

Gast won his first two starts for the Cardinals while going 11 1/3 innings and giving up six earned runs.

"It really does stink, because I was finally getting all three pitches and both sides of the plate working," Gast said. "It was finally starting to click from the beginning of the year."

Blazek joins bullpen as Cards add more depth

LOS ANGELES -- After a 4:30 a.m. CT wakeup call in Springfield, Mo., right-hander Michael Blazek arrived at Dodger Stadium around 11 a.m. PT on Sunday, eager to take his spot in the Cardinals' bullpen.

Blazek becomes the latest youngster to earn a spot on the Cardinals' roster. Since April 29, the Cardinals have given five pitchers -- Seth Maness, Carlos Martinez, John Gast, Tyler Lyons and now Blazek -- their first big league call-up. When Blazek makes his debut, he will become the ninth pitcher aged 25 or younger to pitch for the Cardinals this season.

The Cardinals cleared a spot on the 25-man roster for Blazek by moving left-hander John Gast to the disabled list. Blazek, who will wear No. 67, was already on the 40-man roster, so no additional move had to be made.

"You don't really know what to expect really," Blazek said. "It's still kind of surreal. I'm just trying to keep it the same as much as possible."

Ranked No. 9 among Cardinals prospects, Blazek had been a standout in the Springfield bullpen this season. In 17 appearances (19 2/3 innings), Blazek allowed two earned runs on 11 hits and 10 walks. He struck out 25.

Blazek last pitched on Thursday, meaning that he'll be an available arm for manager Mike Matheny immediately. The Cardinals needed another reliever after asking their bullpen to log seven innings on Saturday. The club chose to add Blazek over other pitchers on the 40-man roster because of how well he was throwing in Double-A.

"We're going with our best guy," Matheny said. "He's been throwing the ball best. We leave a lot up to our development people to take a look at who is throwing the ball well now, and Michael has been throwing the ball well. He has real good stuff and is young and working, but we had some nice reports from Double-A."

Blazek, 24, has been in the Cardinals' organization since being taken in the 35th round of the 2007 First-Year Player Draft. He was used primarily as a starter until transitioning into a bullpen role last season.

Beltran sits with left shoulder soreness

LOS ANGELES -- Carlos Beltran was out of the Cardinals' lineup on Sunday due to left shoulder soreness. Beltran's status is currently considered day-to-day.

Beltran informed the Cardinals' medical staff of the shoulder discomfort midway through Saturday's game. That prompted manager Mike Matheny to replace Beltran with Shane Robinson during a seventh-inning double-switch. Asked if Beltran is expected to be ready to return to the field in Kansas City on Monday, Matheny said, "possibly."

Beltran is a career .299 hitter at Kauffman Stadium, where he played his home games for the first seven years of his career.

"He does a pretty good job of evaluating [his own status]," Matheny said. "I know when he tells me he's dealing with something, I don't push it. I take those opportunities to get somebody else in, and he'll let me know when he's ready to go."

Beltran, hitless in eight at-bats during this series, ranks second in the National League with a .485 batting average with runners in scoring position. He leads the Cardinals with 10 homers and 29 RBIs this year.

Wacha under consideration to start Thursday

LOS ANGELES -- General manager John Mozeliak is scheduled to join the Cardinals on Monday in Kansas City, where he will meet with manager Mike Matheny and the coaching staff to determine who will take the now vacant spot in the rotation.

Though Matheny said that "everybody" is being considered, the legitimate list of candidates is dwindling because of how many roster moves the Cardinals have already had to make this month. Whoever the Cardinals call upon will pitch on Thursday, as that would have been John Gast's next turn in the rotation.

Among those being considered is highly-touted right-hander Michael Wacha, who continues to thrive in his first Triple-A season. Wacha is listed to start for Memphis on Monday, though the Cardinals could choose to keep him out of that game if they want to add him to the big league rotation.

Wacha, the Cardinals' top pick in the 2012 First-Year Player Draft, is 4-0 with a 2.05 ERA in nine starts this season. He has struck out 34, while walking 15 in his first year in Triple-A. He is currently ranked as the organization's fourth-best prospect according to MLB.com.

If the Cardinals are not ready to push Wacha to the Majors, they could consider Memphis starter Maikel Cleto, who is already on the 40-man roster. Joe Kelly, who threw 62 pitches out of the bullpen for St. Louis on Saturday, has not been ruled out as a fill-in option.

Worth noting

• Right-hander Jake Westbrook confirmed that he will have Dr. James Andrews provide a second opinion on his elbow Tuesday in Pensacola, Fla. Westbrook said he continues to be pain-free while throwing on flat ground, but that he wants to get one more set of eyes on his elbow before he again tries to throw off the mound.

"Maybe he can figure out what we can do to get it better," Westbrook said.

• The Cardinals will have a designated hitter spot to fill for two games against the Royals, beginning on Monday. That will give the Cardinals a pair of opportunities to start first baseman Matt Adams, who has made just two starts since April 21. Adams entered Sunday batting .390 in 41 at-bats.

• Missouri native Cedric the Entertainer may have graduated from high school in St. Louis, but he was clad in Dodger blue for Sunday's game. Cedric the Entertainer -- née Cedric Kyles -- threw out a ceremonial first pitch and introduced the Dodgers lineup during the pregame ceremonies.

• The Cardinals are scheduled to face right-handers James Shields (2-5, 2.47 ERA) and Ervin Santana (3-4, 3.14 ERA) in their upcoming two games in Kansas City. That series will be followed by a two-game series against the Royals back in St. Louis.

Jenifer Langosch is a reporter for MLB.com. Read her blog, By Gosh, It's Langosch, and follow her on Twitter @LangoschMLB. This story was not subject to the approval of Major League Baseball or its clubs.