Despite graduations, trades, Astros' new Top 30 strong

General Manager Jeff Luhnow executed his rebuilding plan to perfection. He tore the Astros down and reconstructed them into a World Series champion over six seasons, forming a nucleus around homegrown stars Jose Altuve, Alex Bregman, Carlos Correa, Dallas Keuchel and George Springer. The farm system also contributed postseason hero Lance McCullers Jr. and the trade fodder used to acquire Evan Gattis, Ken Giles, Brian McCann and Justin Verlander.
• Astros Top 30 Prospects list
The system remains in good shape even after all of its graduations and trade departures. Luhnow managed to acquire Verlander last August and Gerrit Cole in January without parting with the organization's two best prospects, right-hander Forrest Whitley and Kyle Tucker, high school first-rounders who should make their presence felt in Houston in the near future (even with Whitley suspended for 50 games after failing a drug test).
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A minor deal that sent Josh Fields to the Dodgers for outfielder/first baseman Yordan Alvarez in July 2016 will pay huge dividends if Alvarez's bat is as good as it looked last season. International signings, both of the big-ticket variety (shortstop Freudis Nova, left-hander Cionel Pérez) and from the bargain bin (right-handers Jorge Alcala and Hector Perez) have helped maintain the system's depth.
Biggest jump/fall
Here are the players whose ranks changed the most from the 2017 preseason list to the 2018 preseason list.
Jump: Jorge Alcala, RHP (2017: 29 | 2018: 7)
Fall: Miguelangel Sierra, SS/2B (2017: 10 | 2018: NR)
Best tools
Players are graded on a 20-80 scouting scale for future tools -- 20-30 is well below average, 40 is below average, 50 is average, 60 is above average and 70-80 is well above average. Players in parentheses also have the same grade.
Hit: 55 -- Kyle Tucker (Yordan Alvarez, Myles Straw)
Power: 60 -- Kyle Tucker
Run: 70 -- Myles Straw
Arm: 70 -- Joe Perez
Defense: 60 -- Gilberto Celestino (Myles Straw)
Fastball: 70 -- Jorge Alcala (J.B. Bukauskas, Jandel Gustave)
Curveball: 65 -- Forrest Whitley
Slider: 65 -- J.B. Bukauskas
Changeup: 55 -- Rogelio Armenteros (Brandon Bailey, David Paulino, Cionel Perez, Forrest Whitley)
Control: 55 -- Rogelio Armenteros (David Paulino, Cionel Perez)

How they were built
Draft: 16
International: 10
Trade: 4
Breakdown by ETA
2018: 7
2019: 7
2020: 10
2021: 6
Breakdown by position
C: 2
1B: 0
2B: 0
3B: 3
SS: 2
OF: 7
RHP: 13
LHP: 3