In the fifth inning of a game against St. Louis on Wednesday, Cincinnati rookie center fielder Billy Hamilton slapped a single to left field against Cardinals right-hander Shelby Miller. For Hamilton, this is the hardest part. At 23, given a chance to be an everyday player, Hamilton must prove that he can get on base enough to remain one. Through eight games, he was hitting just .192 with a .250 on-base percentage. It’s early, but traditionally that wouldn’t be enough.

Still, what happened next shows why Hamilton is already one of the most exciting players to watch.

Hamilton is the fastest player in baseball. It’s not close. And opponents already know it. The first pitch to Brandon Phillips, the next hitter, was a pitchout. Then came a fastball, and Hamilton was off. Catcher Yadier Molina, who has won the past six National League Gold Gloves and has thrown out 44 percent of would-be base stealers in his career — didn’t even attempt a throw.

Phillips then lofted a short fly ball to right. Cardinals right fielder Jon Jay had all his momentum going toward the infield. Yet Hamilton tagged anyway. He made it to third easily.

For all of baseball’s advanced analytics, there’s really no way to consistently quantify this: advancing on a ball on which others couldn’t advance. Which brings us to what happened after Joey Votto walked. With one out and runners at the corners, Jay Bruce popped up into shallow right.

The ball was playable for second baseman Kolten Wong, but Jay called him off — and Hamilton made his move. It’s fairly safe to say no other runner would have attempted this. It’s safer to say no other runner would have scored. Jay’s throw was accurate; Hamilton beat it. Bruce had slammed his bat in frustration, but wound up with a sacrifice fly and an RBI.

Hamilton has already been in and out of the lineup with injuries. In a full 2013 season in Class AAA, his on-base percentage was just .308. Yet in his first 21 major league games (including 13 last year), he reached base 16 times. Including appearances as a pinch runner, he has 15 steals and been thrown out just twice. He has scored 11 runs.

And as Wednesday showed, if he leads off an inning and gets on, he may have a better chance of scoring than any player in baseball — regardless of what the hitters behind him do.