When Theo Epstein and Jed Hoyer took over the Cubs' front office, they were very clear with their goal -- building a foundation for sustained success.

But no team is successful on the free agent market alone. There has to be an influx of talent coming through the farm system, even if those players are only used as a means to an end, a part of a deal to help the major-league club.

So Epstein, Hoyer and senior vice president of scouting player development Jason McLeod have spent a lot of time and effort on building up the farm system, with an eye toward the future. Their project has worked, as ESPN's Keith Law ranked the Cubs' farm system fifth in all of baseball earlier this week.

Law's list of Top 10 Cubs prospects, however, varies drastically from five other rankings we've found from other reputable sites.

Below is a chart of where six major prospect rankings slot 25 different Cubs prospects. In addition to Law, Baseball America and Baseball Prospectus also list only 10 players, while FanGraphs ranks 15 and MLB.com and John Sickels from MinorLeagueBall.com stretch to 20 prospects.

It's no question who the Cubs' top three prospects are. The top picks in the 2011 and 2012 drafts -- Baez and Almora, respectively -- look like the real deal in the early going, while Soler, the Cuban import the Cubs signed last summer, has wowed scouts with his raw talent.

It gets a little murky after those three, however. Some still consider Jackson a Top 10 prospect, but Law didn't even rank him. Maples, a 14th-round draft pick in '11, is also unranked by Law and Baseball America despite Top 10 rankings by the other four outlets.

Vogelbach, a 2011 second-round pick, carries a big frame -- 6-foot, 250-pounds -- that may have scared off Law, but his light-tower power and raw skills with the bat have some other experts drooling.

Law is very high on switch-hitter Candelario, a 19-year-old infielder who finished last season with the Boise Hawks, and Paniagua, who has quite an interesting story.

It's interesting to see the variation between each of the six outlets. Jae-Hoon Ha didn't end up on any lists, but came in at No. 12 on MLB.com's rankings. Vitters, the former third overall pick, is absent from three lists and far down on the other three despite a very good season at Triple-A Iowa last year.

The Cubs' system has come under some heat over the last couple years for a lack of pitching prospects, but that seems to be trending in the opposite direction now. Ten of the 25 players are pitchers, with Maples, Whitenack and Cabrera as the only holdovers from the previous regime.

Noticeably absent from these lists is Trey McNutt, the Cubs' former top pitching prospect. He has fallen on hard times since his breakout 2010 campaign, with a myriad of injuries and even a demotion to the bullpen in Double-A Tennessee last year. His absence may speak more to the lack of impact prospects the system had before Theo and Co. took over.

Of the 25 players on the list, 10 players -- Almora, Soler, Vizcaino, Johnson, Villanueva, Underwood, Blackburn, Paniagua, Loux and Fujikawa -- have been acquired by the new front office. Throw in Anthony Rizzo's graduation to the big-league club last summer and it's a good showing for just 16 months of work.