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9/13/2013 12:29 A.M. ET

Six-man rotation gives Samardzija more rest

PITTSBURGH -- The Cubs have switched to a six-man rotation to give Scott Baker more starts, which should also help Jeff Samardzija.

A year ago, Samardzija was shut down on Sept. 8 after totaling 174 2/3 innings in 28 starts, his first season in the rotation. On Wednesday, he made his career-high 30th start, and now has 194 2/3 innings. He is five strikeouts from 200 for the season.

"He's never been there before," Cubs manager Dale Sveum said of the right-hander, who has given up 17 runs over 18 1/3 innings in his last three outings. "I'm not going to say that's the reason for the struggles. The last two outings [against the Marlins and Reds] have been in the worst heat of the year. Who knows? You don't have the answers for everything. The bottom line is being able to make that pitch."

Building up innings can only help Samardzija next season, Sveum said.

"We didn't baby anything [this season]," Sveum said. "It's the first time an arm and a body and everything has gone through those trials and tribulations of a full Major League season."

Rizzo still fighting through frustrating season

PITTSBURGH -- Anthony Rizzo does have 21 home runs and 73 RBIs this season, but the Cubs first baseman is batting only .228, and there have been longer low streaks than high ones, which is not what he expected coming into the year.

"I could say it's been frustrating," Rizzo said of his season before going 1-for-4 in Thursday's 3-1 loss to the Pirates, "but I've also hit a lot of balls hard and they just haven't found holes. That's the difference between a good season and a bad season. Whatever happens at the end of the year, I'll look back at a lot of positives. In a couple weeks, we'll be talking about the same thing and I'll assess it then."

Actually, Rizzo said he probably wouldn't answer the phone once the season ends. Cubs manager Dale Sveum called this a character building season for the young slugger.

"You don't expect people to hit .300 or hit eight or seven home runs each month," Sveum said. "A lot of people have peaks and valleys. ... That's where we are in his career in his development. [He's going through] the sophomore jinx or whatever you want to call it -- the fact of the matter is, he has 20 home runs and 70 something [RBIs]. The average isn't there or with men in scoring position. It's a learning process."

Would Sveum encourage Rizzo to spend a week in Arizona working on his hitting in the offseason?

"That's up to him," Sveum said. "He might want to get away from it. He might want a change of pace, see what he can come up with -- who knows? It might be a mental block anyway. You get mentally beat down. Sometimes you can blame it on mechanics or this and that, and it's really just your confidence level is so low, it's tough to hit in that situation."

Rizzo said his goal is to simply help the Cubs win.

"You just play baseball," Rizzo said. "It's like any other season, to be honest. We're out of it, so you have to focus on the positives and get the team together and play baseball."

Rizzo has not homered this month, but he does have 35 doubles on the season, fourth most in the National League. So there are positives.

"[The season] got out of hand and the year got away from him," Sveum said. "You say, 'I've got to grind this out and help the team win any way I can. I've got to grind and get through this and make some changes and get my confidence back and move on from there.' The adversity that comes with this game builds a lot of character. You have to wait and see if it does build character."

Castro could be a candidate for leadoff spot

PITTSBURGH -- The Cubs miss David DeJesus, whom they traded earlier this season, at the top of the lineup. So, looking ahead to next season, who might be the Cubs' leadoff man?

It could be Starlin Castro.

"He could be that guy," manager Dale Sveum said before Castro drove in his 40th run with a single in a 3-1 loss to the Pirates on Thursday. "That's where he seems to hit the best. Look throughout all of baseball. It's not the easiest thing to find is a bonafide leadoff guy."

Castro most likely would have to bat .300 to have the on-base percentage needed to fill that spot, as he's walked only 26 times this season

"The way he's been hitting lately, I think he's learned a lot where he could hit at the top of the order," Sveum said.

This season has been a struggle for Castro, who began this year with a career .297 average, but the two-time All-Star is batting .241 with nine home runs and 30 doubles.

"Offensively, he's had his toughest year," Sveum said of the shortstop. "The adversity and how to deal with that is another learning experience in the big leagues. The one thing we know about this game is it's a humbling game and how you get through that is basically it.

"There are only a certain amount of poeple in the history of the game who have gone 18, 20 years who have had good seasons every single year. Everybody will look back and throw one year out in their career. How you handle that and come back shows character. You want to see what happens."

Extra bases

Welington Castillo is tied for 15th among Major League catchers with a .987 fielding percentage, but Sveum has seen his backstop grow in his first full year on the job.

"Welington, to me, is right there with [Yadier] Molina as the top defensive catcher in baseball," Sveum said. "Nobody blocks better, and it's hard to say anybody throws better. He's doing a good job swinging lately, but it's nice to have a catcher who can do a lot of things and he's learned a lot in the last year and a half. He's the whole package.

"He goes into camp next year as a more seasoned veteran where he can concentrate on his offense. There's a lot more in that tank offensively than what we've seen."

Castillo is batting .271 with six home runs and 28 RBIs in 108 games, sharing time with Dioner Navarro.

"Welly has been on another level all year," Rizzo said.

Top prospect Javier Baez led the Cubs' Minor Leagues in home runs and RBIs and right-hander Kyle Hendricks posted the lowest ERA and most wins in the 2013 season.

Baez, the Cubs' first-round pick in the 2011 First-Year Player Draft, hit 37 home runs combined at Class A Advanced Daytona and Double-A Tennessee and finished with 111 RBIs. Class A Boise's Kevin Encarnacion posted the best batting average, hitting .355 for the short-season team. Tennessee's John Andreoli had 40 stolen bases between Daytona and Tennessee.

Hendricks gave up 37 earned runs in 166 1/3 innings for a 2.00 ERA between Tennessee and Iowa, and he finished with 13 wins.

Right-hander Brian Schlitter totaled the most saves in the Cubs' Minor League organization with 22, and Tennessee's Eric Jokisch had the most strikeouts with 137.

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.