PHOENIX -- For the second time since arriving in Arizona, the Cubs swapped one young right-handed reliever for another on Wednesday to freshen their bullpen.

Prior to its series finale with the D-backs, Chicago placed Brian Schlitter (impingement in throwing shoulder) on the 15-day disabled list and recalled Mitch Atkins from Triple-A Iowa to assume his roster spot.

Manager Lou Piniella said Schlitter injured the shoulder in his last outing -- he allowed five runs on Friday against the Reds -- and the cortisone shot he received on Saturday improved his ailment, but not to the degree that he became available out of the bullpen.

Schlitter, who made three appearances since being called up on June 26, will accompany the club to Los Angeles for a four-game game set that closes out of the first half. He will likely be activated to the roster shortly after the All-Star break.

Atkins, who was available to pitch in long relief Wednesday, wasn't called upon in his June 12-15 stint at the big league level. The 24-year-old went 5-2 with a 3.60 ERA in 18 games (10 starts) for Iowa and now joins a 'pen that already includes fellow rookies Andrew Cashner, James Russell and Justin Berg, who was recalled on Monday.

"We need some innings out of our bullpen," Piniella said. "The young kids are going to have to perform."

Especially on Wednesday, Piniella added, because the skipper hopes to avoid using closer Carlos Marmol in the eighth inning after a three-out save on Monday and a five-out save on Tuesday. Piniella also does not want to employ lefty Sean Marshall for more than two batters as he has pitched three innings in the series already.

Castro getting special help from De Jesus

PHOENIX -- Starlin Castro's glove-work needs, well, work.

And he knows it, because first-base coach Ivan De Jesus keeps reminding him.

While bench coach Alan Trammell is another former Major League middle infielder with plenty of wisdom to share, De Jesus, who was the Cubs' shortstop from 1977 to 1981, speaks the language.

Literally.

"I'm Latin and I know his language for the communication," De Jesus said. "That helps a lot.

"We want to make sure he understands what we're saying. That's where I come in say, 'This is what [Trammell] is trying to tell you,' in his own language, so he knows what's going on."

Especially for a 20-year-old who, while he has shown potential with a bat in his hands (.271 batting average with 14 extra-base hits, including two home runs), has yet to prove he can handle the infield's most difficult position. Castro's error in Tuesday's 6-4 win over the hosting D-backs ignited Arizona's two-run eighth-inning rally and was his 12th fielding miscue in 54 games. By comparison, Stephen Drew, the shortstop in the opposing team's dugout, has made three errors in 73 games.

"It's part of the growing pains," said De Jesus, who in his mid-20s averaged 28 errors per season over his five in Chicago.

In fact, Castro has struggled at shortstop throughout his brief career. At Class A Dayton and Double-A Tennessee in 2009, he made 39 errors in 119 games. And prior to his May 7 call-up this season, he had tallied five in 26 for Tennessee.

"We rushed him [to the Major Leagues]," De Jesus said. "He was kind of wild, but now he's settled down a little bit. The more he plays, the better he gets."

In addition to in-game experience, plenty of pregame instruction -- in Spanish, of course -- between the Puerto Rican coach and the Dominican player has proved necessary. When Trammell has advice that is complex in nature, De Jesus takes on the role of translator. Much of their tutelage focuses on pre-at-bat positioning which requires a mental rolodex of batters' scouting reports, being nifty around second base and "making the routine play 99 percent of the time." After all, everyone can agree Castro has the arm strength and range to play the position well.

"By the time we finish the season, hopefully, he's learned all aspects," De Jesus said. "It's not overnight; it's going to take time."

Worth noting

A Cubs official said the team hasn't been able to outline a return schedule for suspended pitcher Carlos Zambrano because his anger management treatment remains ongoing. Zambrano, who has been on the restricted list since a June 25 confrontation with teammate Derrek Lee in the dugout at U.S. Cellular Field, is unlikely to pitch before the All-Star break. He will be returning as a reliever. ... Manager Lou Piniella said he is optimistic that Carlos Silva, who has had soreness behind his right knee would be able to make his final start of the first half on Sunday in Los Angeles. ... Tyler Colvin (1-for-7 thus far on the road trip) wasn't in Piniella's starting lineup on Wednesday. ... Geovany Soto, who was hitting .423 over his past seven games, was slated to bat eighth. ... Piniella on closer Carlos Marmol recording 77 strikeouts in 40 2/3 innings, or 17.04 per nine, which leads Major League relievers: "It's unbelievable. He comes at you with pretty devastating stuff. When he's getting that fastball over and that breaking ball is breaking off of the table, it's a tough combination for hitters to guard against." ... Cubs Minor League pitcher Jeff Samardzija pitched five shutout innings and fanned eight for Triple-A Iowa on Tuesday night.