The dramatic changes the A's made to their Major League roster in the past year have also reshaped their farm system. The top three players on this list a year ago -- Addison Russell, Billy McKinney and Daniel Robertson -- have all been traded away. That hole was filled this winter when the A's acquired seven players now ranked among their top 15 prospects.
With Russell, McKinney and Robertson gone, first baseman Matt Olson has become Oakland's top prospect. While playing with Class A Advanced Stockton in 2014, he led the Minor Leagues in walks (117) and ranked third in home runs (37).
Olson is joined in the top 10 by two of his teammates in Stockton's infield last season, third baseman Renato Nunez and second baseman Chad Pinder. The Ports' infield was rounded out by Robertson.
• Athletics' 2015 Top 30 Prospects list
Biggest jump: Yairo Munoz, SS (2014: Unranked | 2015: 8)
Biggest fall: B.J. Boyd, OF (2014: 12 | 2015: Unranked)
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.
Hit: Franklin Barreto (60)
Power: Matt Olson (65)
Run: Billy Burns (80)
Arm: Matt Chapman (70)
Defense: Chapman (60)
Fastball: R.J. Alvarez (65)
Curveball: Dillon Overton (55)
Slider: Alvarez (55)
Changeup: Overton (55)
Control: Kendall Graveman (55)
How they were built
Rule 5: 1
Breakdown by ETA
Breakdown by position
Teddy Cahill is a reporter for MLB.com. Follow him on Twitter at @tedcahill. This story was not subject to the approval of Major League Baseball or its clubs.