There’s no cheaper commodity in sports than that noxious mixture of potential and hype. Everyone’s selling it, and they’re digging deeper and younger to find it. Draft coverage — pick the sport — often gets more headlines than the games themselves. It’s no longer enough that 16-year-old football players are fêted nationally when they sign letters of commitment — now 13-year-olds are ranked on their ability to play basketball.

America is a nation of optimists. It is part of our cultural DNA to dream that the best is yet to come. And so it is with sports: We believe that somewhere in this great land of ours, there’s a teenager who’s destined to be the best ever at his sport. The best tennis player — Jennifer Capriati was on the cover of Sports Illustrated when she was 13. The best golfer — Michelle Wie was supposed to change the face of women’s golf when she was still in junior high. And even, when our national pride swells to imperial hubris, the best soccer player — remember when Freddy Adu was supposed to change the world? Adu was cast next to Pele in a Nike commercial and featured on 60 Minutes when he was 15 years old. Eight years later, Adu is toiling in Major League Soccer this year, after playing in Turkey in 2011. The Turkish Second Division.

So when Bryce Harper introduced himself to the national consciousness three years ago this month — as the youngest baseball player ever to appear on the cover of SI — it was fair to be skeptical. Of our four major sports, baseball is clearly the one that takes the longest to master. College football players go straight from the draft to NFL stardom. Elite players can jump to the NBA or NHL right out of high school. But even the best college baseball players usually need a year or two of minor league instruction before they debut in the majors. And Harper wasn’t a 21-year-old college junior; he was a 16-year-old kid. To many, that magazine cover set Harper up to fail more spectacularly and visibly than he would have otherwise.

Three years later, Harper evokes another teenage prodigy who was hyped before he achieved anything against the best in his sport. Only now, he’s making his case to be the Tiger Woods of baseball — the child phenom who had unrealistic expectations placed on him and who has not just lived up to them, but has somehow, impossibly, exceeded them.

When Harper became a national figure in 2009, there was a problem — he still had two years of high school left to finish, two years before he could even begin his journey through the minor leagues. Problem solved: He got his GED after his sophomore year and enrolled at the College of Southern Nevada, which would make him eligible for the draft in 2010, while he was still just 17.

The College of Southern Nevada plays in the SWAC conference, where only wooden bats may be used during conference play. This allowed Harper to emulate professional hitters in another way. In his one year at CSN, as one of the youngest college hitters in the nation, Harper hit .443/.526/.987. In 66 games, he hit 31 home runs. The school’s previous record for homers was 12. CSN made it to the Junior College World Series; in the regional championship game, Harper hit four home runs and had 10 RBIs.

After the Nationals drafted him no. 1 overall, Harper took the summer off before Scott Boras negotiated a last-minute, five-year major league contract that guaranteed him $9.9 million, the highest bonus ever for a hitter out of the draft. Harper finally made his pro debut that November, in the Arizona Fall League. Having just turned 18, Harper was the youngest player in the history of the AFL, which is a finishing school for prospects, most of whom had spent the year in Double-A and Triple-A. In nine games, Harper hit .343 and slugged .629.

Harper finally made his official minor league debut last season, and he needed only 72 games — during which he hit .318/.423/.554, swatted 14 homers, and even stole 19 bases — to reach Double-A. Still 18, Harper hit a tepid .256/.329/.395 for six weeks before his season ended a few weeks early with a bad hamstring strain.

This spring, Harper tempted the Nationals to bring him north with the major league team after spring training. Instead, he went to Triple-A and in 20 games hit .250/.333/.375 with a single home run. As hard as this is to believe today, six weeks ago most people in the game thought Harper still needed more development time in the minors.

And then the Nationals called him up to The Show.

When Harper debuted on April 28, he was 19 years, 6 months, and 12 days old. He’s the youngest player to appear in a major league game since Felix Hernandez debuted in 2005 and he’s the youngest position player since Adrian Beltre in 1998. 1 In the last 25 years, the only position players to reach the majors at a younger age have been Alex Rodriguez, Ken Griffey Jr., and Andruw Jones.

That, in itself, is a notable achievement — only four hitters in the last quarter-century reached the majors at a younger age than Harper, and depending on how much credit the electorate gives Jones for his defense, it’s possible all four will wind up in the Hall of Fame. But what’s really notable about Harper is what he’s done since being called up.

After going 3-for-4 with a walk Monday night, Harper is batting .295/.381/.527. He isn’t simply holding his own — he’s dominating. Among players with at least 160 plate appearances, Harper ranks 12th in the NL with a .908 OPS. He has the highest OPS on the Nationals.

Let’s rephrase that: Bryce Harper, age 19, is the best hitter on a first-place team.

His fellow teenage debutants don’t come close to replicating his performance. As a 19-year-old rookie, Beltre hit .215/.278/.369. Jones hit .217/.265/.443 when he was called up in 1996. Rodriguez debuted in the majors while he was still 18, but he was clearly overmatched and hit .204/.241/.204 before he was sent back to the minors. The following year, A-Rod played sparingly and batted .232/.264/.408. Only in 1996, when Rodriguez was 20 (he turned 21 during the season), did he dominate, leading the AL in batting average (.358), doubles (54), runs scored (141), and total bases (379).

In the last 40 years, the only 19-year-old to play regularly and hit at an above-average level was Griffey, who batted a respectable .264/.329/.420 for the Mariners in 1989. Factor in his glove in center field and Griffey was a well-above-average player — but at the plate, Harper has clearly been better.

In fact, with one exception, Harper has out-hit every teenager in major league history. Here is a list of the highest OPS by a teenager (minimum: 150 plate appearances) going back to 1876:

Year Age Name OPS 1928 19 Mel Ott .921 2012 19 Bryce Harper .908 1964 19 Tony Conigliaro .883 1951 19 Mickey Mantle .792 1970 19 Cesar Cedeno .790

Ignore, for a moment, the names on the list, and just consider Harper’s place on it. Bryce Harper is in the midst of a season that is almost without precedent in MLB’s 126-year history.

Now, with only 39 games under his belt, it’s possible that Harper is simply in an unsustainable hot stretch, and that by year’s end his numbers may drop into more pedestrian territory. But Harper has built up such a lead that he’s likely to stay on this list even with some regression to the mean. Griffey, for instance, didn’t have a .908 OPS in any single month of his rookie season. Harper has played so well for so long that there’s no other way to characterize what he’s doing but to call it historic.

Mike Trout, the wunderkind who is making his case as the best player in the American League at the age of 20, hit just .220/.281/.390 last season, when he was 19. Trout is having a historic season in his own right, but even he couldn’t match Harper’s exploits as a teenager.

OK, back to the names. Mel Ott’s a Hall of Famer, and Mickey Mantle was apparently a ballplayer of some renown. (Harper wears no. 34 in homage to the Mick, because 3 + 4 = 7.) But Conigliaro was never the same after he took a fastball to the temple in 1967 — inspiring a very different sort of SI cover — that caused him to miss the next 18 months. Cedeno was on a Hall of Fame trajectory into his mid-20s, but by the time he reached 30 he was a shell of his former self.

Just because Harper is an All-Star caliber ballplayer at age 19 doesn’t mean he’s guaranteed to scale greater heights as he ages. If anything, by setting the bar so high at such a young age, he has created such high expectations that he could become one of the signature players of his generation and still leave people wanting more. (In unrelated news, the NBA Finals get under way tonight.) Not even Harper has raised the realm of possibility as much as Kerry Wood did the day he struck out 20 Astros in just his fifth major league game. Wood’s retirement last month, with just 86 wins and 63 saves to his credit, is a fitting reminder of how much can go wrong even after a player reaches the summit.

Except for one major distinction: Wood was a pitcher, and pitchers — especially young pitchers — get hurt. Moreover, their injuries have a nasty way of eventually robbing them of their ability to pitch. Hitters don’t get hurt as often, and their injuries rarely cause permanent impairment to their abilities.

Let’s take a look at a couple of charts. Here is a list of the 12 pitchers in the live ball era (since 1920) with the most career wins by their age 22 season:

Pitcher Wins Career Wins Hall of Fame? Bob Feller 107 266 Yes Dwight Gooden 73 194 No Bert Blyleven 63 287 Yes Larry Dierker 55 139 No Mike McCormick 54 134 No Milt Pappas 53 209 No Frank Tanana 51 240 No Don Drysdale 51 209 Yes Fernando Valenzuela 49 173 No Gary Nolan 49 110 No Don Gullett 48 109 No Wes Ferrell 46 193 No

By definition, every pitcher on the list was a phenom in his youth, and yet the majority of them are remembered more for what might have been than for what was. Too many pitches at too young an age ended the careers of Dierker, Nolan, and Gullett by the time they turned 30. Tanana and Valenzuela hung on as crafty finesse pitchers as they aged. Gooden tore his rotator cuff when he was 24 and was never the same. Even the success stories were finished early. Drysdale threw his last pitch two weeks after he turned 33. Bob Feller, still (and probably always) the greatest baseball phenom ever, lost his fastball in his early 30s and won his last game at 36. Bert Blyleven is the only pitcher on that list to stay effective into his late 30s.

Now here’s a list of the 12 hitters with the most hits through their age 22 season:

Name Hits Career Hits Hall of Fame? Buddy Lewis 753 1563 No Robin Yount 717 3142 Yes Mel Ott 715 2876 Yes Al Kaline 710 3007 Yes Freddie Lindstrom 689 1747 Yes Ken Griffey Jr. 652 2781 Probably Alex Rodriguez 648 2834+ Probably Vada Pinson 626 2757 No Cesar Cedeno 618 2087 No Edgar Renteria 611 2327 Probably not Ted Williams 563 2654 Yes Mickey Mantle 561 2415 Yes

It’s not really a comparison. Two-thirds of the players on this list are or will be Hall of Famers — granted, Lindstrom’s induction was a joke — and three of the other four players had long and generally satisfying careers. Buddy Lewis is forgotten today, but he was one of the AL’s best third basemen before serving three years as a pilot in World War II, and he retired soon after returning from the war, while still a valuable player.

If you extend these lists the differences become even more stark. Of the 25 winningest pitchers through the age of 22, just six made the Hall of Fame. (C.C. Sabathia and Felix Hernandez have a chance to make it eight.) Of the 25 hitters with the most hits through age 22, 18 of them — counting Griffey and Rodriguez — are Hall of Famers. Being a productive everyday player in the majors at a very early age doesn’t guarantee that you’ll go on to a Hall of Fame career — but it comes awfully close.

Since we’re talking about Bryce Harper, one more list is relevant here — the list of the 12 hitters with the most home runs by age 22:

Name HR Career HR Hall of Fame? Mel Ott 115 511 Yes Eddie Mathews 112 512 Yes Alex Rodriguez 106 638+ Probably Tony Conigliaro 104 166 No Frank Robinson 98 586 Yes Bob Horner 91 218 No Ted Williams 91 521 Yes Ken Griffey Jr. 87 630 Probably Johnny Bench 87 389 Yes Jimmie Foxx 86 534 Yes Mickey Mantle 84 536 Yes Al Kaline 82 399 Yes

While there’s a lot of overlap, this list is even more impressive than the last one. Conigliaro got hurt, and Bob Horner got fat — but every other player on this list is a Hall of Famer. There is no stronger indicator of a Hall of Fame career than precocious power — the very skill Bryce Harper is most famous for.

It seems that only two things can prevent a hitter who has reached Harper’s level from going on to a Hall of Fame career. The first is a serious injury. The pitch that eventually cost Conigliaro the vision in his left eye still resonates a half-century later. Cesar Cedeno suffered a severe ankle injury in the 1980 NLCS and was never the same.

It’s also possible that a player might simply lack the drive to achieve greatness. Cedeno was questioned about his work ethic for much of his career. Horner ate his way to Japan by the time he was 29. Andruw Jones, who would rank next on the home run list with 80 homers by age 22, was notorious for his laissez-faire attitude toward practice, which might explain why he suddenly appeared washed-up at the age of 31 before reinventing himself as a platoon corner outfielder.

There’s no way to guard against injuries, but if there’s one thing no one worries about with Bryce Harper, it’s whether he has the desire to be great. For a while, there were actually worries that his desire to be great might get him killed. The kid bought eye black by the barrel, and his team was eliminated from the Junior College World Series after he was suspended for arguing with an umpire. In the minor leagues last year, Harper caught heat for hitting a home run and then blowing a kiss at the pitcher. His reputation preceded him — when Harper was introduced during his major league debut in Los Angeles, he was booed. Lustily.

But since reaching the majors, Harper has only shown up his opponents with his bat, his legs, and his arm. It’s as if he finally decided to respect his opponents once he reached a level of competition where he felt they were worthy of his respect. He has been a model citizen as a major leaguer, having done nothing more egregious than deliberately knocking off his helmet while cruising into second base on his first major league hit. He took the high road when Cole Hamels hit him with a pitch and bragged that he did so to put the rookie in his place.

While Harper has behaved himself, he has also played balls-to-the-wall day in and day out. After Hamels plunked him, Harper served revenge on a straight steal — of home. Harper has good speed but is hardly a burner, yet he has already hit four triples in a little more than a month, the sign of a player who’s thinking extra bases every time he comes out of the box.

He makes adjustments quickly; last Tuesday, after striking out badly in the 11th against Elvin Ramirez, he faced Ramirez again with the bases loaded and two outs in the 12th, and after falling behind 0-and-2, Harper served a line drive to left field for the first walk-off hit of his career. He has a flare for the dramatic. On Sunday, Harper wasn’t in the starting lineup for the first time since he was called up. Instead, he pinch-hit in the ninth inning of a tie game, drew a walk, then streaked around from first on a two-out double to plate the winning run.

Bryce Harper is 19 years old. He’s been in the major leagues for six weeks. He’s accomplished almost nothing. And yet he’s proven almost everything. Sometimes the hype machine gets one right, and sometimes the hype machine is even a little understated. If you find him to be infuriating, we suggest you find a way to learn to live with him. It looks like he’s going to be with us for a long, long time.