The Chicago Cubs are reportedly working to lock up young shortstop Starlin Castro with discussions for a long-term extension ongoing. Castro is a fast-rising star for the Cubs and has been one of the bright spots in an otherwise ugly season as they work on a rebuild. Theo Epstein, the architect of that rebuild, is planning to have Castro signed to a long-term extensions before the end of the 2012 season, according to David Kaplan of CSNChicago.com.

Kaplan cites two sources who indicated that the deal is being discussed and would likely be for six or seven years, wiping out his arbitration-eligible years and likely adding two more years of control from when Castro was originally supposed to hit the open market. Here's what one source told Kaplan about the move:

"If Castro continues to develop into one of the best shortstops in baseball and he reaches free agency in four years, he will be unbelievably expensive to retain for the Cubs," the source told me. "This is very smart business by Theo Epstein and Jed Hoyer. They will know what their costs are for a significant amount of time going forward and for Castro, he will have lifetime security rather than going year-to-year during arbitration until he completes six full years in the game."

Castro is currently hitting .276 with 12 homers and 58 RBIs. Along with Anthony Rizzo, he figures to be a cornerstone in Esptein's rebuilding efforts in Wrigleyville.

For more on the Cubs and their contract talks with Castro, visit Bleed Cubbie Blue.