It is rarer still -- a once-a-generation type of occurrence -- when two athletes arrive simultaneously, leaving scouts and insiders swooning. That's what Mike Trout and Bryce Harper have accomplished on opposite coasts, in Southern California and Washington, respectively.
As with Harper, his teammate with the Scottsdale Scorpions of the Arizona Fall League last October, Trout leaves no questions unanswered with his skill set. It is off the charts, across the board.
Coming from Bruce Springsteen's New Jersey turf, Trout was born to run. He can fly. He's disciplined at the plate, with the ability to work counts and slash line drives to all fields while occasionally going beyond 400 feet with a power stroke. He covers mounds of ground and has exceptional instincts in the field and on the basepaths. If he has one skill that isn't graded as a plus, it's his arm. But that, too, is developing.
Trout made it to the Major Leagues last year at 19 -- struggling the first time around, looking like a seasoned pro when he was recalled. He is back showing his stuff, a year wiser, despite missing much of Spring Training with what was described as a respiratory virus.
In part because of that late start and an outfield packed with proven talent, Trout opened the season at Triple-A Salt Lake. He skipped that level while spending most of 2011 at Double-A Arkansas when he wasn't playing a bench role in Anaheim.
Abusing Pacific Coast League pitchers with a .403/.467/.623 slash line in 20 games, Trout was summoned to Anaheim on April 28 with center fielder Peter Bourjos struggling offensively.
Even though he didn't come out smoking, Trout remained confident in his approach and is finding his footing of late. This is where his makeup comes into the picture. Here is a self-assured -- if not cocky -- athlete, convinced that he will succeed at the highest level.
This profile also fits Harper, who has more power and a stronger arm than his buddy, Trout, but is not quite as fast. Harper kicked up a storm at Dodger Stadium with a sensational debut and has continued to generate electricity for the Nationals.
Trout, a Type A personality, needs only to control his aggression to regain the approach that took his Minor League on-base percentage to .425. This has management confident that he can become a superb catalyst.
"Leading off is something I've been doing my whole life," said Trout, who has taken that role since his arrival. "I've just got to get on base and score some runs."
It is possible in the not-so-distant future to anticipate Harper challenging for home run and RBI crowns in the National League while Trout is contending for batting and stolen-base titles.
The consensus of scouts is that, like Mantle and Mays, they'll be seeing each other frequently at All-Star Games and perhaps in a World Series or two.
For Angels manager Mike Scioscia, it was love at first sight with Trout, taken in the first round of the 2009 First-Year Player Draft with the 25th overall pick, acquired from the Yankees as compensation for their free-agent signing of Mark Teixeira.
While the Angels see Trout evolving into a weapon at the top of the order, he could be equally dangerous as a No. 2 or No. 3 hitter if Bourjos assumes the leadoff role. This would give Scioscia two of baseball's fastest players in the top third of the order.
"There's still growth coming with Mike," Scioscia said. "He's been remarkable coming out of high school to where he is now. You're not going to see many guys who put it together as quickly. At every level as you go up you have to make adjustments."
Trout has experience at all three outfield positions. He figures eventually to settle in left or right given Bourjos' superior range of defensive talents.
Trout lasted deep in the Draft primarily because of the relatively light exposure he received playing on the East Coast with its inclement weather.
It quickly became distressingly clear to a majority of clubs that they'd erred in judgment. Top pick Stephen Strasburg is the only player from that '09 Draft who figures to be in Trout's class over the long haul.
Trout was a dominant pitcher in addition to playing shortstop and the outfield at Millville (N.J.) High School. A running quarterback who also excelled in basketball, he was clocked by scouts in 6.38 at 60 yards. Anything 6.5 and under is plus speed.
"That 6.38 is a scout's timing -- we're not electronic," former scouting director Eddie Bane said after the Draft. "But you see few guys get under 6.5.
"Trout is faster than most everybody else in the Draft -- and he's put together. He's the first guy from that area ever to go in the first round, so they're really excited back in Jersey. His dad, Jeff, played in the Minor Leagues when I was playing. Mike comes from a real baseball family and environment."
Jeff Trout made it as high as Double-A, a second baseman in the Twins' organization, and has molded and prepared his talented son.
"He's always telling me what I'm going to go through," Trout said. "He hit it on the nose the first couple years."
Ultimately, Trout figures to be more of a blend of Henderson -- the greatest leadoff man ever -- and Rose than The Mick or Mays. Along with Rickey's speed, Trout owns Henderson's solidly constructed frame and plays with the intensity and abandon of "Charlie Hustle."
Trout has been somewhat guarded with the media, not wanting to add to the extraordinary hype of ranking among the game's top three prospects. He was rated No. 1 by MLB.com last season.
"I'm just trying to play my game and help the team win," he said. "That's all I'm thinking about now."
He'll be content to let his actions speak for him until he's established. If scouts, numbers crunchers and other baseball lifers are correct in their appraisals, he'll be shouting from the rooftops for years to come.
Lyle Spencer is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.