ATLANTA -- It wasn't a good 25th birthday for pitcher Casey Coleman, who was optioned to Triple-A Iowa on Tuesday to make room on the roster for pitcher Chris Volstad.

Coleman was 0-1 with a 7.32 ERA in 16 relief outings with the Cubs, and 2-3 with a 3.48 ERA in seven appearances, including six starts, with Iowa.

Volstad, who was in the Cubs' rotation at the start of the season but optioned to Iowa after going 0-6 with a 7.46 ERA in eight starts, started Tuesday night against the Braves.

Barney to keep aggressive approach in field

ATLANTA -- When Steve Clevenger starts at first base, he positions himself near the bag and draws a line in the dirt next to his right foot. Clevenger jokes that he's responsible for the small area to the left of that line. Cubs second baseman Darwin Barney has everything else.

Barney has made so many acrobatic plays lately, it's hard to keep up. In Monday's 4-1 win over the Braves, he made two spinning catches on back-to-back plays in the eighth.

"That's about as good as it gets," Cubs manager Dale Sveum said Tuesday of his second baseman's highlights. "Those kind of plays and the defense he's had all season long are incredible. It's hard to believe there's been a better second baseman in baseball this year than Barney. Maybe somebody as good, but not better, that's for sure."

Barney entered Tuesday's game with a 66-game errorless streak, totaling 543 1/3 innings. His last miscue was in the eighth inning April 17 in Miami. The last Cubs middle infielder with a longer streak was Mike Fontenot, who had a 90-game stretch from May 7, 2008-June 30, 2009.

"I wouldn't say it's important," Barney said of his streak. "Just contributing is important. Obviously, there are goals, and one of my goals that [infield coach Pat Listach] and I talked about is trying to win accolades defensively, which isn't easy to do.

"The one to get is the Gold Glove. It's been said it's an offensive award, it's been said it's a Rawlings award -- I don't wear Rawlings. If there's anything that's kind of where my sights are, that's it more than my errorless streak."

He wants to be aggressive and realizes that approach could result in errors.

"There was a line drive the other day and I caught it and threw it to first really fast, and that's the kind of play I'm not not going to make because of something like that. I'm still going to be aggressive."

Listach has been key in helping Barney with his positioning. They study spray charts on hitters. But the second baseman still has to be athletic to get to balls.

"It's his double-play turns, it's just everything -- his work ethic and a guy who goes out there every single day to try to be a Gold Glover, a real Gold Glover," Sveum said.

"The positioning is helping a lot," Barney said. "It's putting us in a better situation to succeed against guys. But more than that, it puts you in a defensive mindset. You're moving around and trying to get in a perfect spot. If I have a different feeling for a guy than [Listach] does, I'm going to move. This game is all about intuition and people moving guys. It gets your head in the game on a defensive level."

Has he told rookie first baseman Anthony Rizzo to get out of his way?

"Not really," Barney said. "I like my first basemen to go after everything. I don't want them to assume I'm going to get to a ball. ... Someone as athletic as Rizzo, I'd rather he goes hard until I call him off."

Barney isn't going for the personal recognition.

"Let's win 20 in a row and be back in the hunt," he said. "That's kind of what the goal is, more than anything personal. Right now we're playing well and playing good defense and getting timely hitting. Who knows?"

Cubs ink 18 of first 20 Draft picks, 27 overall

ATLANTA -- The Cubs have signed 18 of their first 20 picks, and 27 players overall selected in the 2012 First-Year Player Draft, including right-handed pitcher Ryan McNeil of Nipomo (Calif.) High School, who was selected in the third round.

In addition to McNeil, the list of new Cubs signees includes right-handed pitcher Trey Lang (sixth round), right-handed pitcher Justin Amlung (12th round) and infielder David Bote (18th round).

McNeil, 18, logged a 1.10 ERA and held the opposition to a .175 batting average last season for Nipomo High School. He struck out 94 in 57 1/3 innings pitched, good for an average of 14.76 strikeouts per nine innings, while walking just 21. The 6-foot-3, 210-pound McNeil hit .392 with four doubles, a triple, two home runs and 18 RBIs.

Still unsigned is outfielder Albert Almora, the Cubs' first-round selection, as well as second-round pick Duane Underwood, who threw at Wrigley Field over the weekend.

Extra bases

• Cubs pitcher Ryan Dempster will have his second bullpen session in three days on Wednesday at Turner Field, and then be re-evaluated Thursday to determine the next step.

Dempster, sidelined with a sore right lat, threw 40 pitches off the mound Monday, and had no problems.

The Cubs hope to set the rotation for their first series after the All-Star break against the Diamondbacks, July 13-15, once they know how Dempster is feeling.

• Anthony Rizzo recorded the game-winning RBI in three of his first five games, becoming the first Cubs player in franchise history to accomplish the feat since the RBI was made an official stat in 1920. Of his five RBIs, four have given the Cubs the lead, and the other has tied the game.