© 2014 MLB Advanced Media, L.P. All rights reserved.

7/16/2014 12:55 P.M. ET

Cubs' youth movement beginning to accelerate

Prospect promotion, rotation opportunities things to watch for in second half

CHICAGO -- In his first year as the Cubs manager, Rick Renteria has had to find a new closer, deal with the loss of two starting pitchers who were traded, and juggle the lineup after his leadoff man was injured.

Midterm Report 2014
At the break
Club breakdowns
First-half highlights

One constant from the previous two seasons is that the Cubs find themselves last in the National League Central going into the All-Star break. It's all part of the rebuilding process underway at Wrigley Field.

It seems as if Renteria has been asked more questions about the Minor Leaguers than the big league squad. Will Cubs fans see the top prospects in the second half? Arismendy Alcantara,  who has been impressive since he was promoted from Triple-A Iowa, is expected to stay for at least the first series of the second half. We'll see.

Five key developments

1. Starlin Castro is back
After a difficult 2013, when he hit .245, Castro rebounded to earn another All-Star nod. The shortstop has thrived in the cleanup spot and played better defense. He's worked hard, and it's paid off.

2. Anthony Rizzo can hit left-handers
Southpaws held Rizzo to a .189 average last year, but this season, he's produced a higher batting average vs. left-handed pitchers than right-handers. Rizzo also has bounced back from a difficult first full season in the big leagues.

First-half awards
MVP: Starlin Castro
Castro bounced back from a difficult 2013, and leads the team in RBIs and made the All-Star team for the third time in his young career.
Top starter: Jeff Samardzija
He ranked among the NL leaders in ERA, and was named to the NL All-Star team one day after he was traded to the Athletics.
Top rookie: Neil Ramirez
Ramirez has 34 strikeouts in 25 2/3 innings, and did so well, he was considered for save situations and could be a future closer.
Top reliever: Hector Rondon
Rondon was pressed into the closer's role when Jose Veras struggled, and has been learning on the job.

3. Jake Arrieta has ace potential
Arrieta was slowed this spring by tightness in his right shoulder and the cautious approach has paid off. In back to back starts, he had a no-hitter through six innings. With Jeff Samardzija and Jason Hammel gone via trade, Arrieta is now No. 1 in rotation.

4. The Cubs still need a closer
Jose Veras didn't work and was released. Kyuji Fujikawa is still rehabbing from Tommy John surgery. Neil Ramirez is still developing. Hector Rondon is learning on the job.

5. Edwin Jackson continues to be an enigma
Jackson has the same amount of losses (10) at the All-Star break this season as he did a year ago at the break. And a year ago, he led the NL in losses with 18. It's been puzzling.

Five storylines for second half

1. Will young pitchers take advantage of opportunities?
With Samardzija and Hammel gone, the Cubs have two openings and the options include Dallas Beeler, Kyle Hendricks, Tsuyoshi Wada, Chris Rusin and newly acquired Dan Straily. Let the auditions begin. The Cubs need a fourth starter on July 22.

2. Which one of top prospects gets to the big leagues first?
Alcantara was called up to sub for Darwin Barney, and he did so well, the team decided to keep him more than the originally planned two days. Who's next? The Cubs have said Kris Bryant, who is leading the Minor Leagues in home runs, will stay at Triple-A Iowa. Is Javier Baez ready? This season, the spotlight has been on the kids more than the big league team, and it's likely to continue.

Players to watch in second half
3B Mike Olt
Olt led all National League rookies at the All-Star break in home runs (12), and has played solid defensively, but he was batting .144 with 79 strikeouts.
OF Junior Lake
Lake ranks among the NL leaders in strikeouts, which would be fine if he were a pitcher, but he's not.
2B Arismendy Alcantara
In his first five big league games, Alcantara was 9-for-23 with a home run, three doubles, a triple and five RBIs. Cubs fans want more.

3. Who will be traded next?
The Cubs jumped the market by dealing Samardzija and Hammel on the Fourth of July, and they'll likely be active right up to the Trade Deadline. Teams are looking at infielders like Luis Valbuena and Barney, as well as some of the Cubs' relievers. That can create some anxiety in the clubhouse.

4. Can Mike Olt reach the Mendoza Line?
Olt finished the first half leading all NL rookies in home runs and RBIs, but he wasn't close to batting his weight. The good news is that Olt is healthy. He needs to make the mental adjustments to deal with big league pitching.

5. Can they find a closer?
The Cubs do have some power arms in the bullpen in Rondon, Ramirez, Pedro Strop and Brian Schlitter . They're hoping one of their in-house candidates emerges as the man to get the final out.

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.