For every Mike Trout who dominates from his first full year in the big leagues, Major League Baseball tests the staying power of dozens of hitters whose progress is measured in baby steps. The challenge might come in the form of injuries, a loss of confidence or a weakness that can be easily exploited by opposing pitchers with the ability to execute a scouting report.
The operative phrases are "growth pains" and "learning curve."
"I say this all the time, but this game is punch and counterpunch," Cincinnati Reds manager Bryan Price said. "A young player can come up and perform very well, but the game always counters. It doesn't matter who you are.
"The game is going to find out that you struggle with the ball in, or you struggle more with the curveball than the slider, or you don't recognize the changeup, or you can't lay off the high fastball. The league comes back and has success against guys, and the good ones adjust."
Jackie Bradley Jr. has attracted a lot of national attention for his turnaround story in Boston this season. The five hitters below, who range in age from 24 to 29, have navigated plenty of setbacks and come out looking good. Now they're in the conversation for All-Star berths and enjoying breakout seasons.
How did they get here, why are they succeeding, and what level of performance can their teams expect in the years to come?
Adam Duvall, Cincinnati Reds (21 homers and a .580 slugging percentage)
Duvall is, by all accounts, a hard worker and conscientious teammate with zero sense of entitlement. He also makes quite a first impression.
"He has such strong wrists and hands," Reds broadcaster Chris Welsh said. "It's like shaking hands with a cinder block."
As a former 11th-round pick who signed with San Francisco for a $2,500 bonus out of the University of Louisville in 2010, Duvall was never hyped. Even after he hit 30 homers for Class-A San Jose in 2012, he peaked at No. 11 on Baseball America's list of the Giants' top 30 prospects. The primary knocks against Duvall: lack of speed and high error totals at third base.
Cincinnati acquired Duvall in a July 2015 trade for Mike Leake, and he seized his opportunity by beating out Scott Schebler for the Reds' everyday left field job. Duvall's 76-to-12 strikeout-to-walk ratio is worrisome, but he's improved his all-fields approach thanks to extensive tee work at the behest of Reds hitting coach Don Long. Of Duvall's 21 homers, six have gone to center field or the opposite way.
"The thing that excites me about Adam's future is, he already has an approach that closes up some holes a lot of young players have," Price said. "He has the ability to stay on pitches out over the plate. He can get the barrel on the ball on the inside and compete against breaking balls, especially with two strikes.
"I think we have a player who can be a good one for an extended period."
Duvall's glove has been almost as big a revelation as his bat. He ranks second to Pittsburgh's Starling Marte among left fielders with nine defensive runs saved, and he's shown an accurate arm and the aptitude to hit cutoff men. He's more than a one-dimensional player.
"I think this is real," one scout said. "He's a better baseball athlete than his body or reputation would lead you to believe. There's going to be some regression. I don't know if he's going to be a .260 hitter with 40 home runs.
"But I think he'll be a .235-to-.250 guy who's a threat to hit 25 to 30 [homers] playing 81 games in that park. Who the hell wouldn't want that guy, especially if he can continue to do what he's done in the outfield?"
Michael Saunders, Toronto Blue Jays (.291/.367/.563 slash line in 254 at-bats)
Saunders teased the Seattle Mariners for years with his athleticism and natural gifts, but he spent enough time on the disabled list to get tagged with the injury-prone label -- or a rap among some scouts as "soft." Toronto acquired Saunders in a December 2014 trade for pitcher J.A. Happ, and Saunders literally got off on the wrong foot with his new team when he stepped on a sprinkler head in spring training of 2015 and tore cartilage in his left knee.
This February, Saunders' name came up as part of a proposed three-team trade that would have sent him to Anaheim and resulted in Jay Bruce leaving Cincinnati for Toronto. The talks collapsed and the trade never materialized.
"I'm sure the rumors were very difficult," Blue Jays general manager Ross Atkins said, "but Michael has been very selfless in the way he's handled everything. It was never 'woe is me.' He's been very professional, and he's always been focused on wanting to be a Toronto Blue Jay."
At age 29, Saunders is outdoing Dustin Ackley, Brad Miller and other former Seattle prospects who have yet to benefit from their changes of scenery. His 13 extra base hits and 1.004 OPS against left-handers are testament to his ability to hang in the box versus lefties. Thanks to improved plate coverage, six of his 15 homers have gone to center field or the opposite way.
Saunders benefits from hitting in a stacked Toronto lineup, and his .360 batting average on balls in play suggests some regression is on the horizon.
"He's having a good three months," said one scout who's withholding judgment. "When he does it for a full year, I'll come on board."
That said, Saunders' strong start puts him in a position to land a nice free-agent payday this winter where he could be an attractive option as an athletic, left-handed outfield bat.
Wil Myers, San Diego Padres (17 homers, .520 slugging percentage, 2.4 WAR)
You could argue that Myers already had his breakout season in 2013, when he slashed .293/.354/.478 in 88 games with Tampa Bay to win the American League Rookie of the Year award.
That was before a series of wrist injuries sapped Myers' power, and the Rays packed him off in December 2014 and the Padres gave him a test run in center field. Myers grew sufficiently tired of the criticism to develop a bit of a chip on his shoulder.
Now he's settled in at first base, and he has matured as a hitter to the point where he can get fooled badly by a pitch and then punish the same pitch later in the same at-bat. Myers also has become more adept at using the entire field. Of his first 83 hits this season, 37.6 percent went to left field, 37.6 percent went to center, and 24.8 percent went to right.
"Everybody I've always talked to says he's a good kid, and he's obviously gifted," a National League scout said. "But he's kind of a laid-back kid, and I think he took some stuff for granted. There's a level of maturity going on with him now that I hadn't seen the last couple of years.
"I've written him up as quality regular and a part-time All-Star. Over the next four or five years, none of us should be surprised if he's hitting .270 with 20-25 home runs and 90 RBIs. That's certainly a part of what he can be."
Marcell Ozuna, Miami Marlins (.320 batting average, 16 homers, .948 OPS)
Aspiring trade partners swarmed the Marlins with proposals last winter amid reports that Ozuna had fallen out of favor with owner Jeffrey Loria. The Marlins insisted on top-of-the-rotation-starter types when clubs were trying to peddle them No. 4 and No. 5 starters. In talks with the Mariners, Miami pushed for Taijuan Walker when Seattle was thinking more along the lines of Nate Karns or Roenis Elias.
This is a classic case of the best trade being one an organization never made. Ozuna, who's been bothered by a wrist injury of late, is tied with Gregory Polanco and Carlos Gonzalez for sixth among NL outfielders with a 2.3 WAR. Ozuna, Christian Yelich and Ichiro Suzuki have given the Marlins premium outfield production to help offset Giancarlo Stanton's slow start.
Ozuna also has benefited from standing closer to the plate and improving his plate coverage. In his first three big league seasons, he hit .199 with a .564 OPS against pitches on the outer third of the plate. This year, he's batting .293 with an OPS of .808 on those same pitches.
Both Marlins officials and MLB talent evaluators trace Ozuna's numbers in part to a greater commitment to conditioning this season.
"The kid was overweight last year," said a scout. "He wasn't in the shape he needed to be in, and he wasn't the same cat. But the bat speed and ability have always been there.
"Where would that team be without him right now?"
Gregory Polanco, Pittsburgh Pirates (.296/.375/.515 in 72 games)
Pittsburgh's esteemed Latin scouting director, Rene Gayo, signed Polanco for $175,000 out of the Dominican Republic and projected him as an outfielder when talent evaluators thought Polanco's best route to the majors was as a pitcher. Polanco stands 6-5, 230 pounds and has massive power potential from the left side, so the early Darryl Strawberry and Dave Parker comparisons were inevitable.
Pittsburgh GM Neal Huntington concedes the Pirates probably rushed Polanco to the majors two years ago when they summoned him from Triple-A Indianapolis even though he had played a mere 130 games at Double-A ball or higher. After a dazzling start, Polanco faded to .235 in 89 games as a rookie.
With the benefit of time and experience, Polanco has done a better job turning on hard stuff inside and driving it with authority. He's slugging .632 on fastballs on the inner third of the plate this season, compared to .372 in his first two seasons.
"Because of the length of his levers, he has to work hard to stay short and compact through the ball, and to stay inside the ball," Huntington said. "As he's done that more consistently, he's been more successful.
"He's so big and physical, and he's still growing into his body. That's the fun part about it. There's still maturation and growth here, but he's kept his athleticism. He still runs well. The ball jumps off his bat, and he can hit pitches in different parts of the zone. He's got aptitude and intelligence, and he has a feel for what teams are trying to do. It's all beginning to come together for him."