Toolshed: What future may hold for callups

The prospects are coming! The prospects are coming!
It has been a big week for promotions, with three of the game's top 35 overall prospects moving up to the Major Leagues since Tuesday: Rockies infielder Brendan Rodgers (No. 10), Brewers second baseman Keston Hiura (No. 15) and Braves third baseman-turned-outfielder Austin Riley (No. 34). What's more, No. 58 Corbin Martin made his first start for the Astros on Sunday. That also doesn't include the debuts of other notable prospects like Shaun Anderson (Giants), Jared Walsh (Angels,) Nicky Lopez (Royals), Oscar Mercado (Indians) and Cole Irvin (Phillies) -- each of whom were sent to The Show since the week began.
It's enough to make any prospect prognosticator's head spin. To set things back straight, this Friday's Toolshed predicts the best- and worst-case scenarios for the remainder of the 2019 season for each of the four Top-100 prospects who've just seen the bright lights of the Majors for the first time.

Brendan Rodgers
Best case: Rodgers finally brings some stability to a Colorado infield that has found it in short supply for much of the season's first two months. The 22-year-old shows that his .356/.421/.644 line at Triple-A wasn't solely a product of playing his games in the Pacific Coast League, and he makes a quick transition to hitting Major League pitching. When Trevor Story shows full health, Rodgers takes over second-base duties from Ryan McMahon and holds them down all summer, even after a healthy Daniel Murphy is ready to play again every day. The position becomes one less thing Colorado has to worry about in its pursuit of a third straight postseason appearance.
Worst case: Rodgers usually takes some time to adjust to a new level. He produced a .260/.323/.413 line over 38 games with Double-A Hartford after his first move there in 2017 and put up just a .554 OPS in his first taste of Triple-A last season. That continues in the Majors, and it becomes harder for the Rockies to justify an everyday spot for the rookie, especially when everyone is healthy. He bounces back and forth between Denver and Albuquerque and doesn't stay up for longer than two weeks until rosters expand in September, at which point the then-out-of-contention Rockies play him for evaluation purposes.

Keston Hiura
Best case: Hiura is what he's been pretty much his entire life -- one of the best hitters wherever he is. The 2017 first-rounder hits the ground running -- or rather raking -- and never really stops, putting up one of the best batting averages among eligible rookies in 2019. What's more, he shows his power jump at Triple-A San Antonio (11 homers in 37 games) was no joke, and he becomes a splendid right-handed addition to an offense that already features Christian Yelich, Mike Moustakas, Lorenzo Cain, Ryan Braun, Yasmani Grandal and Jesús Aguilar -- giving Milwaukee one of the strongest lineups in the game. Hiura's impact is enough to give the Brewers their second straight division title, and Hiura is in the upper half of the lineup in Game 1 of the NLDS. Even after missing out on the first quarter of the season, he pushes the likes of Pete Alonso, Chris Paddack, Fernando Tatis Jr. and Mike Soroka for NL Rookie of the Year honors.
Worst case: Major League pitchers find holes in Hiura's swing that their Minor League counterparts could not. It happened with Vladimir Guerrero Jr. initially, remember, and unlike the Blue Jays, the Brewers can't afford to let a youngster find his footing. Wanting to give him everyday at-bats, the club moves its top prospect back to San Antonio when Travis Shaw returns from his wrist injury, and with that in the past, the veteran rediscovers his offensive form. With Hiura not good enough defensively to justify jumping over a hot Shaw and an out-of-position Moustakas, he sticks in San Antonio until late in the second half, when he's brought up again as a bench bat. 

Austin Riley
Best case: The Braves' No. 4 prospect has a bit more cut out for him in terms of solidifying his immediate spot with the Major League club, but he's got the power to take this first opportunity and run with it. (Reminder: he was tied for the Minor League lead with 15 homers at the time of his promotion from Triple-A Gwinnett, and 10 of those had come in his last 13 games alone.) Riley continues to pulverize the ball and becomes Atlanta's best power option alongside Freddie Freeman and Josh Donaldson. He plays good enough defense in left field that Ender Inciarte, who has a .623 OPS this season, is moved to a bench role to allow Riley to continue to shine. The right-handed slugger finishes with 20-plus homers and an OPS around .900.
Worst case: Like Rodgers, Riley has historically taken some time to adjust to a new level, and that continues in the Majors as he gets fooled consistently while flirting with a 30-35% strikeout rate. Because he only played left field four times before getting summoned to The Show, his defense also remains a question mark. It becomes clear to Atlanta that it can live with a lesser bat in Inciarte if he can return to his Gold Glove form in center, thus pushing Riley back to Gwinnett. Donaldson stays healthy all summer, meaning Riley isn't able to take over at his natural position at third base. The 22-year-old ends the season with his rookie status still intact, unable to pick up enough at-bats or days on the active roster to graduate.

Corbin Martin
Best case: The 23-year-old right-hander jumped the line a bit by posting a 1.48 ERA and 1.03 WHIP with 28 strikeouts and 11 walks over five appearances (24 1/3 innings) with Triple-A Round Rock and looked every bit the part of a Major League starter when he struck out nine and allowed two earned runs over 5 1/3 innings while averaging 95.7 mph with his fastball against the Rangers on Sunday. Houston moved Collin McHugh to the bullpen to make room for Martin, so it's willing to carve out a role for him. Under this best-case scenario, that arrangement continues as Martin's arsenal -- including a plus fastball and above-average curveball and slider -- keeps Major League hitters guessing with each passing turn in the rotation. Martin overtakes Wade Miley as the Astros' No. 3 starter, and after Houston runs away with the AL West, he starts Game 3 of the ALDS behind Justin Verlander and Gerrit Cole. 
Worst case: Forrest Whitley looms large in the Astros organization, even if he is off to a rough start in his first taste of Triple-A. As Major League hitters get more videotape of Martin and his tendencies, the right-hander's performance begins to dip just as Whitley returns to form. With the 21-year-old having the higher ceiling of the two, the Astros allow Whitley to take a crack, and with his own deep package of pitches, he's the one that thrives. The Astros keep Martin in the Round Rock rotation to keep him lengthened out until late in the second half, when he becomes this year's version of Josh James in the bullpen during the final month.