We waited a little longer than we would’ve liked, but the day is finally here: Pittsburgh Pirates shortstop Konnor Griffin is set to make his MLB debut on Friday afternoon. Griffin isn’t just the consensus top prospect in baseball; he has the chance to be a truly generational player, a combination of size, speed and athleticism so rare that the Pirates didn’t even wait for him to play in a big-league game before they handed him $140 million over the next nine years.

Just how impressive has he been since being drafted No. 9 overall in the 2024 MLB Draft? Griffin has reached the doorstep of the Majors before even reaching his 20th birthday. When he takes the field on Friday against the Baltimore Orioles on Friday, he’ll be just 19 years and 344 days old, placing him in one of the more exclusive fraternities in baseball history.

The youngest rookies in modern MLB history

In the early years of the 20th century, when baseball was a very different sport played by very different athletes (and there wasn’t nearly the developmental pipeline both college and the Minors), teenagers breaking into MLB was a relatively common occurrence. Heck, the youngest player in Major League history, Joe Nuxhall, was 15 years old when he broke in with the Reds back in 1944.

A lot has changed since then, to say the least. Big-league players have only gotten better and better, and thus it’s gotten harder and harder to physically compete. The most recent teenage debut was Juan Soto for the Nationals in 2018, and suffice to say he’s the exception rather than the rule. Below is the complete list of players who have appeared in a big-league game before turning 20 — and as you can see, it’s some pretty select company.

Sure, not every player here is a star. But you’d be hard-pressed to find someone who was good enough to play Major League baseball at such a young age and didn’t go on to have at least a moderately successful career. Even the lesser names on this list, guys like Betemit and Karim Garcia, played for at least a decade — and that’s the floor.

The ceiling is much higher. From Soto to Bryce Harper, Mike Trout to Felix Hernandez, Adrian Beltre to Alex Rodriguez, a disproportionate number of teenagers in the Majors wound up becoming superstars when all was said and done. It’s not hard to figure out why: If you’re not only big, strong and fast enough but also skilled enough to be competing at the highest level at age 18 or 19, just imagine how good you’ll be by the time you start hitting your physical prime? There are exceptions here, like injury (Bundy) and off-field concerns (Urias); other than that, though, the track record is pretty great.

What to expect from Konnor Griffin in his Pirates debut

Rodriguez might be the most interesting comparison to make here. Like Griffin, he was a physical freak, a spectacular defender at shortstop despite having size (standing 6-foot-3) more typically associated with a corner spot. A-Rod was a more highly regarded prep prospect than Griffin was — he was the No. 1 pick with a bullet in the 1993 draft out of Miami’s Westminster Christian — but the two blew through the Minors with similar speed and ruthless efficiency.

Griffin didn’t appear in a Minor League game in the summer after he was drafted in 2024. But from the moment he debuted in 2025, it was clear he was different: Across three different levels, he slashed .333/.415/.527, with 21 homers and 65 steals in just 122 games. And in a brief Triple-A stint to start this season, he posted an OPS near 1.200 with three doubles and more walks than strikeouts in five games.

There’s no question about Griffin’s athletic profile. Like Rodriguez, he’s built like a linebacker at 6-foot-3 and 222 pounds, and his top-of-the-scale speed makes him a positive defender at both shortstop and center field. The only thing that remained to be seen was whether he would hit enough against elite pitching to get all those tools into games on a consistent basis.

That was what led the Pirates to ultimately decide to send him back to the Minors at the end of spring training rather than let him start on Opening Day, as he hit below the Mendoza Line and was swinging at just about everything even close to the strike zone (and some pitches that weren’t). But the ease which which he conquered Triple-A, and the way he was able to adjust and close the holes in his swing across just one full pro season in 2025, suggests that there’s pretty much nothing he can’t do if given a little runway.