As it turns out, however, he didn't give up the educational path at all.
Kelly spends these spring days as a full-time student. There are tutoring sessions from Yadier Molina and staff members in the morning as Kelly, now 19, continues the transition from infielder to catcher. Notetaking comes after the on-field work is done. Then there is calculus homework to complete, a step toward getting the college degree that he promised his parents he would pursue.
Kelly is a cerebral type, eager to immerse himself in learning and thoughtful in his actions. Those intangibles are among the reasons why the Cardinals felt comfortable putting this latest test in front of him.
"He is a real student of the game," said Cardinals director of player development Gary LaRocque. "Carson is the kind of young man who views every day as, 'How am I going to get better?' And now this [catching] opportunity is in front of him and we really feel good about the project."
Perhaps the greatest compliment Kelly could receive this spring came earlier this week when a member of the Cardinals' front office noted that Kelly had not stood out so far. For a teenager who began catching just five months ago, fitting in is the objective.
He is less than two years removed from playing in high school, where the Cardinals zeroed in on him as a potential high-round pick. As they did, they saw a player with tools that could serve him well at several different positions. Kelly was pitching and playing shortstop at the time. Once drafted, the Cardinals had him get comfortable at third.
The challenge to make this next switch came last September, on the first day of instructional league. The Cardinals believed Kelly had the work ethic to pull it off and the aptitude to excel. The opportunity to add value to a budding player was something the organization did not want to pass up.
Kelly recalled his reaction to the news as "a little surprised, but excited."
LaRocque told Kelly that the move would begin as a three-week test run. After that, it would be Kelly's decision whether to continue with the conversion. That was more time than Kelly would need.
About 10 days into the work, Kelly approached LaRocque to ask him what he should tell a reporter who wanted to know if the move was permanent. LaRocque flipped the question to Kelly, who responded: "Oh, I want to catch."
That's when the Cardinals knew Kelly owned the conversion.
"It was absolutely perfect," LaRocque said. "Since that time, he has taken to it, and we're very pleased about how he has approached it."
The early lessons came in instructional league, when Kelly fitted himself for a catcher's mitt for the first time since his pre-high school playing days. The work continued into the offseason and included a trip to St. Louis, where Kelly received one-on-one instruction from manager and former Gold Glove catcher Mike Matheny.
Matheny invited Kelly out to his home; the two also met at Busch Stadium to talk technique.
"It won't take you very long as you talk to him to realize that he just has a demeanor, he has some leadership qualities [and] a lot of attributes that you look for in a young player behind the plate," Matheny said. "He's a learner. He loves to take it all in. He's constantly taking notes and figuring out what he can do to help himself out here. He's made a real good first impression."
It was during that early January visit that Matheny also informed Kelly of the big league Spring Training invitation that awaited him.
"It kind of took me back," Kelly recalled, who added that now that he's here, "it's almost like I don't want to leave the clubhouse every day. I just want to stay in there. The camaraderie among the guys, it's truly a blessing. And it gives you the drive to want to get in there even more. "
This is certainly an ideal environment for Kelly to learn the nuances of the new position. He has a manager ready to invest in him and the game's best catcher available as a resource. It was Molina, Kelly said, who gave him the most lasting piece of advice so far: "We train to be the best. We don't just train to train. We are a family. We help each other out."
Molina has played the latter part out.
"He's a great teacher," Kelly said of Molina, who he has shadowed during certain drills. "He communicates with me and tells me what I need to work on. A lot of the things he has told me have really helped me so far. I'm taking in the information, trying to process it so that I can then go out there and perform. But I understand that it is going to take some time and that it's a long process. Really, it's just taking it all in and then being as quick as I can to put it all into play."
Just a week into workouts, the pupil has already impressed the teacher.
"I'm just happy with the way he works because he wants to learn and is always listening," Molina said. "He's observant. He likes to watch. He asks me a lot of things. And the way he works, you can see that he wants it. He wants to get better. He really wants to be good."
Receiving and blocking have been two particular points of emphasis for Kelly, who has to wait for Spring Training games to work on pitch calling. He's paying close attention to each of the pitchers he catches, too. He writes his own scouting reports in a notebook that also includes pages of notes he's taken since being drafted.
He has written about adjustments, successes and failures, and he has jotted down impactful observations and advice. It was his process-oriented dad, Kelly said, who encouraged him to document the journey.
"The big thing he's doing is he is taking it all in," LaRocque said. "He's working and he's watching and he's listening and he's around our veterans. He's a very, very sharp young man. He's going to put all the work in, but he's also going to learn the way and be respectful of the process. We have absolutely no second thoughts that his development is going to be right on track now."
The Cardinals are not yet ready to publically project where Kelly will begin the season. He could open the year, as he did the last one, in extended spring training, which would allow for additional instruction time. Once he left there, Kelly split the 2013 season with Class A Peoria and Class A Short-Season State College. Facing mostly senior competition in both leagues, Kelly combined to hit .257/.322/.357 with 22 doubles and 53 runs scored in 113 games.
Wherever Kelly plays, the Cardinals do not plan to have him make spot starts at third base. The conversion is a single-sighted mission.
It is not, however, the only item on Kelly's personal to-do list. He fits school into his schedule, too, and this semester that means there are courses in calculus and health to complete. Kelly will earn sophomore status by the summer, and his hope is that in six years, he'll be graduating with a degree in Economics.
"I'm just going to keep plugging away," Kelly said. "It's definitely tough, because you're here at six in the morning, you get your work done and you want to go back and just relax. I have an hour and a half of calculus work to do. But education is very important to me."
And Kelly knows, there are plenty more courses to come.
"The Cardinals have been truly awesome to me and have given me this opportunity," Kelly said. "They invested in me, and I'm very excited for what the future holds. I'm going to keep working hard, and hopefully I'll be in that locker room for good in a few years."