The Cubs have marketed Starlin Castro as a building block, a cornerstone player fans can watch and root for during the rebuilding process.
Cubs president of baseball operations Theo Epstein and his front office staff are all about identifying core players and have given the fanbase assurance by locking up Castro (eight years, $60.1 million) and Anthony Rizzo (seven years, $41 million) through the rest of their 20s.
The hope is Castro and Rizzo will be performing at a consistently elite level -- both in the field and at the plate -- when the Cubs are ready to contend. While Rizzo is having an All-Star-caliber season (.275, 10 HR, 30 RBI), Castro is not quite there yet and his manager is pushing for more.
"His potential is what he wants it to be," Dale Sveum said Sunday. "That's up to him. He's got all the ability to be top-of-the-line, but the rest of it is up to him from now on."
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Castro is only 23, but is already in his fourth big league season and has 579 hits to his name. Like any young player, there are still holes in his game.
After an 0-for-9 stretch to close out the weekend, the two-time All-Star saw his OPS (on-base plus slugging percentage) dip to .692, more than 50 points below his career mark (.756). He also committed his sixth error of the season Saturday and is on pace for 23 miscues. While that would come in as the lowest total of his career, it would still rank near the bottom of the league.
Castro has drawn just 107 walks in 2,103 career plate appearances and is on pace for only 26 free passes this year, which would represent the lowest mark of his career. However, he is seeing 3.83 pitches per plate appearance, which ranks seventh among qualifying shortstops in Major League Baseball.
"It's a little noticeable," Sveum said Sunday of Castro's improvement in taking pitches. "But then you'll have at-bats like yesterday where we're breaking down concentration-wise and we're not getting a good pitch. He's swinging at everything the pitcher throws up there. It just comes and goes. That's what we're talking about as far as the concentration level. It has to be on a consistent basis to get to that next level.
"That's what we got right now in Castro. He's gonna swing the bat. He's only walked  times the whole season. We know what we're going to get."
For his part, Castro admitted he could work the count more.
"Sometimes, I need to take pitches, but today I felt good," he said after Sunday's 4-3 loss to the Mets. "I hit the ball hard twice. That's the only thing I can do -- hit the ball hard. I don't have control of it [after that]."
Castro's concentration has been called into question over his career, including a much-publicized moment in 2011 when ESPN analyst Bobby Valentine ripped the young shortstop on national TV for zoning out during a pitch.
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But it is easy to forget just how young Castro is. He's played in almost 500 MLB games, but is the same age -- or younger -- than most of the game's top prospects. He's still four years away from his physical prime (usually acknowledged to be age 27 through age 31 or 32).
"[He hasn't progressed] as much as we would like to see," Sveum said. "There's still the lapses. Mentally, he's gotten a lot better, but physically, we're still seeing a lot of the same stuff.
"When you get to this level and have played this much, it's up to him how good he wants to be."