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9/1/2013 7:30 P.M. ET

Schierholtz having career year in platoon role

CHICAGO -- Nate Schierholtz finished the month of August with a team-high 19 RBIs for the Cubs, and leads the team this season with a .283 batting average with runners in scoring position.

Schierholtz has 20 home runs and 62 RBIs in 113 games this season. He's platooned in right, getting the majority of starts against right-handed pitchers and has been productive. This year, Schierholtz has set career highs in home runs, RBIs, doubles (26), and at-bats (383).

"He's obviously platooned and did a great job against right-handed pitching," Cubs manager Dale Sveum said. "It's what we expected and couldn't really ask for much more. A 20-home run season and about 65 RBIs, and the equivalent to that if he played every single day would be 30 [home runs] and almost 100 RBIs. That's a very productive season and he's done a great job both defensively and offensively."

Schierholtz and Anthony Rizzo have both reached the 20-home run mark, and they are the Cubs' first left-handed hitters to do so since Rick Monday (26 home runs) and Billy Williams (20) in 1973. Schierholtz and Rizzo also are the third left-handed-hitting duo in the Majors with 20 homers each, joining the Reds' Jay Bruce (26) and Joey Votto (20), and the Mariners' Raul Ibanez (25) and Kyle Seager (21).

Sweeney, Valbuena return from DL; Cabrera recalled

CHICAGO -- Cubs outfielder Ryan Sweeney and third baseman Luis Valbuena were activated from the disabled list, and right-hander Alberto Cabrera was recalled from Triple-A Iowa on Sunday.

To make room for Sweeney on the 40-man roster, right-hander Eduardo Sanchez was designated for assignment.

Sweeney, 28, returns after suffering a left rib fracture when he crashed into the center-field wall on June 29 in Seattle. He was batting .295 at the time with four home runs and 15 RBIs in 44 games.

"To be able to play every day again was huge," Sweeney said of the opportunity he had before he was injured. "To have a freak thing happen like that is definitely not something you want to have happen."

Will he be careful in the outfield?

"I'll remain aggressive," he said. "It's a bone that should be healed. I'm still going to run into the wall if I have to -- unfortunately."

"Hopefully his elbow doesn't get in the way of his ribs this time [if he does]," Cubs manager Dale Sveum said when told Sweeney will keep running into walls. "It's nice to have those guys back, and get the left-handed bats in there."

Sveum plans to rotate Sweeney, Brian Bogusevic, Junior Lake and Nate Schierholtz in the outfield, with Schierholtz getting the majority of playing time against right-handed pitchers.

Valbuena, 27, was placed on the disabled list on Aug. 4 with a right oblique strain. He was batting .225 with 13 doubles, nine home runs and 31 RBIs in 89 games. He will share third with Donnie Murphy, who led the team with eight home runs in August, and Cody Ransom.

"I want to finish strong, that's what I'm looking for now," Valbuena said. "Everybody works a lot and everybody's focused to win the last month and have a good record. That's important right now."

The Cubs aren't set at third base next season. Valbuena could be a candidate.

"I have to be ready for spring and see what decision they make," he said.

Cabrera, 24, returns for his second season with the Cubs after splitting this year with Double-A Tennessee and Iowa. He combined to go 10-6 with a 3.79 ERA in 33 appearances, including 18 starts. He made his Major League debut with the Cubs last August, going 1-1 with a 5.40 ERA in 25 relief appearances.

Sanchez, 24, went 0-1 with a 5.68 ERA in four relief appearances with the Cubs this season. He was claimed off waivers from the Cardinals on May 21 and combined to go 1-1 with three saves and a 3.38 ERA in 33 relief appearances between Triple-A Iowa and Triple-A Memphis.

With the moves, the Cubs' 40-man roster is at 40 players. They are expected to add a few more pitchers once Iowa's season ends on Monday.

Amid rough season, Castro heating up

CHICAGO -- Starlin Castro had multihit games in three of his last four games heading into Sunday's contest against the Phillies, which is encouraging for the Cubs shortstop, who has struggled this season.

After Saturday's game, when Castro hit a tiebreaking solo home run in the sixth, he said he just wanted to "be me" and go back to the swing and approach he had his first two seasons in the Majors when he batted .300. He entered Sunday's game batting .242 this year.

"There's been a lot of [talk] about seeing more pitches and walking more and on-base percentage," Cubs manager Dale Sveum said of conversations with Castro. "As much as anything, that's why I thought I'd get him back in the leadoff spot, the one spot he's most comfortable and had the most success at, and so far he's been driving the ball better and swinging the bat better in that spot."

Castro has batted everywhere but fourth this season, and was hitting .271 (16-for-59) in the leadoff spot entering Sunday. Maybe he just needs to keep it simple?

"There are hitters out there who don't need a lot of thought process," Sveum said. "They're cutters and slashers, and whether they'll be that their whole careers or adjust to be something else, [you don't know]. Sometimes, you adjust and it just doesn't work that easy."

Jackson, Vitters don't get callup consideration

CHICAGO -- Last year, the Cubs promoted past first-round Draft picks Brett Jackson and Josh Vitters to the big leagues in August, but neither one was a consideration for a September callup this season.

Both Jackson and Vitters have battled injuries this year. After batting .223 in 61 games with Triple-A Iowa, Jackson went to Arizona to rehab, and was then assigned to Double-A Tennessee, where he is batting .191 in 28 games.

Vitters has been limited to 28 games at Iowa, and is batting .295, but he's gotten only 88 at-bats.

The Cubs' callups so far have been two players activated from the disabled list (Ryan Sweeney and Luis Valbuena), and right-handed reliever Alberto Cabrera from Iowa.

"We don't have the young kids who are coming up like last year with Brett Jackson and Vitters," Cubs manager Dale Sveum said. "This year, we have some older guys, some left-handed bats who are obviously in the mix for next year and we want to look at and evaluate."

Vitters was the Cubs' first-round Draft pick in 2007, while Jackson was the first-round selection in 2009. Where they fit into the Cubs' plans is still to be determined.

"Things have changed a great deal with them missing so much time this year," Sveum said. "The player-development part of this year has been pretty much lost for both of them. It'll be a wait-and-see thing this winter."

Extra bases

James Russell made his 70th appearance on Sunday and is the fifth Cubs left-handed reliever to record multiple 70-game seasons.

Russell appeared in 77 games last season, and joins Paul Assenmacher (1990-92), Sean Marshall (2010-11), Chuck McElroy (1991-92) and Bob Patterson (1996-97) as southpaw relievers to reach 70 appearances in multiple seasons.

Anthony Rizzo hit his 34th double of the season on Sunday, and is tied for fourth in the National League.

Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.