CHICAGO -- Cubs manager Dale Sveum started working with Starlin Castro right away in Spring Training, and the way the shortstop responded was part of the motivation in signing him to a long-term contract.

"The work [Castro] put in on his defense with the new coaching staff was a big part of what made us feel comfortable extending him for as long as we did," said Cubs general manager Jed Hoyer, who announced Castro's seven-year, $60 million contract extension on Tuesday. "He did have to put work in and make adjustments, and he did that."

Castro does lead all Major League shortstops in errors with 21, but Sveum said there's been significant improvement on how he's handled routine plays and how he's improved the accuracy of his throws.

The next step is to work on improving his pitch selection and patience at the plate. Since Castro has been slotted in the fifth spot in the lineup, Sveum said the shortstop was batting about .400 with runners in scoring position.

"He's taken to that role and had more concentration in that role," Sveum said.

Now that the deal is done, the focus for the final stretch is strictly baseball.

"It'll be interesting to see if there's any change now that this thing is behind him," Sveum said. "Hopefully, it does relax him. Being a young kid and knowing there's a lot of money and years coming his way as a Chicago Cub, I don't care who you are, 22, and knowing all of this has been going on, it has to have been a little bit of a burden."

Cubs activate Parker, designate Hinshaw

CHICAGO -- The Cubs activated right-hander Blake Parker from the 60-day disabled list on Tuesday to add a fresh arm to the bullpen. Left-hander Alex Hinshaw was designated for assignment to make room on the roster.

Parker, 27, had been on the DL since June 6 with a right elbow stress reaction. He was called up from Triple-A Iowa on May 17 to make his Major League debut, and did not give up an earned run over 4 1/3 innings in four outings.

He made eight rehab appearances with Triple-A Iowa and gave up six earned runs over 10 2/3 innings, striking out 13 and walking one.

Hinshaw was claimed off waivers from the Padres on Aug. 19, and gave up five runs over one-third of an inning in two appearances. On Monday, he gave up five runs on four hits and failed to retire any of the five batters he faced.

Cubs manager Dale Sveum said the bullpen was in pretty good shape on Tuesday despite needing outfielder Joe Mather in the ninth inning on Monday. Mather faced two batters and threw four pitches. He gave up a single to pinch-hitter Jeff Bianchi and got pinch-hitter Martin Maldonado to end the inning with a groundout. Milwaukee scored nine runs in the frame.

Barney matches Eckstein's errorless record

CHICAGO -- The Cubs' Darwin Barney played his 113th errorless game Tuesday night in Chicago's 4-1 loss against the Brewers to match a National League single-season record for consecutive games without an error by a second baseman, set by the Padres' David Eckstein in 2010.

The American League single-season errorless streak record for a second baseman is held by Placido Polanco, who went 141 games without a miscue in 2007 for the Tigers.

"When I was younger, I always thought that defense was my weakness, so I put a lot of effort into working on it and getting as solid as I could," Barney said.

This is his second full season as a second baseman, and he's worked on making the transition from shortstop.

"We came in with a plan to fix some things and the plays I had trouble with, and we've secured that up," Barney said.

Barney's 113-game errorless streak at second base spans 910 1/3 innings since his only 2012 miscue at second base, April 17 in Miami. Hall of Famer Ryne Sandberg held the previous Cubs single-season mark of 90 straight games without a miscue at second from June 21, 1989, through the end of the season. Sandberg's streak was part of his franchise record 123-game errorless stretch that ran through May 17, 1990.

On Tuesday, Barney helped turn a double play in the first, and caught Ryan Braun's pop up in the sixth. The second baseman also was part of a rundown in the eighth that led to a Brewers run.