JUPITER, Fla. -- His future in St. Louis now secured, Paul DeJong is eyeing what's next. He has a vision of the type of player he can become; for what the next six, maybe seven, maybe eight years look like in red and white. And it hinges, well, on his vision, both in a literal and metaphorical sense. What he sees. How he recognizes. What he's looking for going forward, and the pitches whizzing towards him at the plate.

"For me right now," said DeJong of what he needs to work on, "managing the strike zone is the No. 1 key."

DeJong knows his ability to master the zone will determine whether or not he reaches his goals. He has lofty ones. The 24-year-old wants 30 home runs in his sophomore season, even though no Cardinals shortstop has ever hit that many in the franchise's 127-year history. He wants to drive in 100 runs. He wants to hit .300. He wants to do all this at shortstop, where only six players have ever done so -- among them Ernie Banks, Cal Ripken Jr. and Alex Rodriguez.

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The Cardinals and DeJong both believe he's close. Maybe not to those Hall of Famers, but to the production plateaus they reached in their illustrious careers. DeJong says the secret to getting to those big numbers lies in the edges of the zone, in the narrow lane between passivity and patience. So that's where he's thrown the lion's share of his focus after a rookie season where he showed a precocious offensive skillset -- and its one glaring hole.

Plate discipline.

Had he accumulated enough at-bats to qualify, DeJong would have ranked as one of baseball's most impatient hitters last season. He hit 25 home runs, slugged .532 and finished second in the National League Rookie of the Year Award voting. But it all came in the shadow of a 4.7 percent walk rate and a 124/21 strikeout-to-walk ratio, which would have ranked fourth and 11th lowest in baseball, respectively.

Beside from the time he's spent signing contract extensions, this spring has been an exercise in improving in the area of plate discipline for DeJong. "Controlling my intentions," he calls it, to which he means improving his ability to dictate counts and at-bats.

Each morning, DeJong is part of a group of players who track their entire first round of batting practice off a machine randomizing speed, spin and location. DeJong's inclusion in the group is intentional.

"He was chosen," Cardinals hitting coach John Mabry said.

For subsequent rounds, DeJong will position himself extra close to a machine spitting out curves, to simulate the recognition of hanging breaking balls. Fastball rounds are often taken with little use of his legs, with DeJong eschewing his lower half in favor of what amounts to a high-velocity game of pepper.

"Hand and barrel accuracy is really what I'm focusing on," DeJong said.

He's also working on improving his hand-eye coordination, so when he does get his preferred pitch, he less often misses it. The shortstop recently inquired with an eye doctor about getting contacts to improve his vision, which already measures at 20/15.

"It's not against the rules to improve your eyes," DeJong said. "I read somewhere that the difference between some Major Leaguers and Minor League players is strictly vision."

The Cardinals showed how they view him on Monday, when the club committed to DeJong with an extension that could keep him in St. Louis through 2025, despite the less than full year of service time to his name. Club officials have valued his intellect since convincing DeJong to hold off on medical school when they used a fourth-round Draft selection with him in 2015, their eyes widening as the former biochemistry major skyrocketed through their farm system.

"One thing that stood out about Paul was his intelligence and his ability to adapt and adjust," president of baseball operations John Mozeliak said. "Anytime you talk about a player who moves as quickly as he did, then the success he had at the Major League level, and then the aptitude to make adjustments and learn, is something we all value and are very impressed with."

A few more minor adjustments could mean the next level for DeJong, whom the Cardinals consider their most cerebral player.

"It's more about the process and the day to day: What happened and why did it happen?" DeJong said. "Hopefully, by the end of the season we'll be saying, 'I managed the zone better, I got more walks, and in the end it was a better year."'