On a list of great 19 year olds in major league baseball (the lack of caps is because I want to avoid fights about whether certain leagues were or were not major in the way that the American League in 2012 is a Major League) is a fellow by the name of Paul Hines
who's pretty unlikely to be known to you unless you already cared about 1870s baseball, in which case you're probably not going to learn anything new here.
Anyway, Paul Hines came up for a godawful Washington Nationals team (as in 8-42 over two years bad) for a couple years, where he was the only remotely good player even as a teenager, before moving on to a merely mediocre Chicago White Stockings team for which he was outstanding, especially considering he was 19 at the time. After a few years there and a league collapse, he had his best season for the Providence Grays, where he won the Triple Crown in 1878. The catch is that at the time, he wasn't recognized as having won any of the 3 components of the Triple Crown.
You see, at that point, RsBI wouldn't even exist as a statistical category for at least a few years. There seems to be some controversy about whether Ernest Lanigan
[who had a ridiculous career, by the way] actually invented it or just popularized it around the fin de siecle, but in any case, Paul Hines was not recognized as the leader in them at the time. Home runs, of course, were very rare at the time and barely figured into the minds of fans, kind of like triples do today. As for batting average, that was a stat that was noted at the time, but the calculations at the time were off and awarded a different man the batting crown. Hines followed that year up with another just as good, and has a legitimate case to be entered into the Hall of Fame, but the honor of having achieved something that was totally unrecognized at the time is probably even rarer than that.