Thwack. OH. Thwack. OHHH.

I arrived on the backfields of Roger Dean Chevrolet Stadium one March morning in 2022, hoping to catch a few rounds of Jordan Walker batting practice. The then-19-year-old was in his first Cardinals Major League Spring Training camp on a non-roster invite and was spending those first few days rubbing elbows with the likes of Paul Goldschmidt, Nolan Arenado, Tyler O’Neill and others in Jupiter. One helper pointed me in the direction of where Walker was expected to take to the cage, but added another detail.

Just listen. You’ll be able to hear him anyways.

So I did. So did everyone within earshot, including multiple Major Leaguers. (They were the ones yelling “OH” after all.) It was one of the most popular BP sessions of the morning from a fan and team perspective as everyone gathered to see what made the 6-foot-6 right-handed slugger such a promising prospect.

• MLB Pipeline | Top 100 prospects | Prospect video

Twelve months later, not much has changed about Walker as a hitter, except this -- he is now a Major Leaguer. The Cardinals confirmed that their top prospect will be on the club’s Opening Day roster this Thursday at home against the Blue Jays. At 20 years and 312 days old, he’ll be the youngest St. Louis player to debut on Opening Day since Steve Carlton in 1965.

• From Decatur to St. Louis: How Jordan Walker made it to the Show

Batting from a slightly open stance, Walker stands intimidatingly tall in the box but stays back on the ball, allowing his size and strength to do the talking on contact. His 115.9 mph double on March 17 stands up as the fourth-highest exit velocity measured by Statcast this spring; the only three higher come from EV king Giancarlo Stanton (118.6, 116.1) and Ryan McMahon (117.7). Expanding the sample some, 16 of his 37 batted balls (43.2 percent) in Grapefruit League play have exceeded the hard-hit standard of 95 mph, putting his hard-hit rate in line with the numbers O’Neill (43.3) and Arenado (38.9) put up in the bigs in 2022.

In 2022, Walker was the only player aged 20 or younger to exceed 500 plate appearances at Double-A, and he did so while hitting .306/.388/.510 with 19 homers and 22 steals in 119 games with Springfield. He got additional time in the Arizona Fall League, where he was the circuit’s top-ranked prospect, and showed out there too. While Statcast was limited to games played at Salt River Fields, Walker still registered the top four -- and five of the top six -- exit velocities in the prospect showcase circuit, topping out at 112.7 mph on Oct. 10.

Based on his performance to this point, Walker could be a 30-plus homer threat for multiple seasons in the Major Leagues.

If there’s anything that could be considered his offensive Kryptonite, it’s breaking stuff low and away. Given his size and upright stance, he can get caught chasing those difficult pitches to hit out of the zone, and Major Leaguers could take advantage.

While there will be plenty of focus on the Georgia native’s offensive game, his defensive work will perhaps be most closely monitored under the MLB microscope.

The Cards moved Walker from third base to the outfield last August to get out from behind Arenado on the depth chart, and his arm strength certainly plays from the grass. He topped out with a 99.5 mph seed in the AFL last autumn, which would be the hardest throw by a Cardinals outfielder since Statcast began measuring in 2015, and added another throw measured at 95.7 mph this spring.

He’s a solid runner underway too and more athletic than his size alone would indicate, also helping to ease the transition. Where Walker will be tested most is in his reads and routes to the ball in the corners, and those will only improve with the reps he’ll get at both corners at the Major League level. He could also rotate through DH to give Dylan Carlson and fellow Top 100 prospect Alec Burleson time on the grass alongside O’Neill and Lars Nootbaar.

This is all to say nothing of his infectious personality off the diamond as a young player who is confident in his abilities, willing to adjust and learn and able to be a leader in any clubhouse.

Want to know what makes Walker one of the game’s best young talents from the moment he debuts? Whether it’s with a bat in his hands or a microphone in front of him, it comes down to those same two words: Just listen.