This report comes via MLB.com's Bill Ladson's blog; Ladson writes also for the Nationals website:
The Nationals are in need of a third-base coach because Pat Listach is leaving the organization to become the bench coach of the Cubs, according to two baseball sources. An official announcement will be made after the World Series.
Listach, Nationals general manager Mike Rizzo and manager Jim Riggleman were not available for comment. It's not known who will replace Listach as Washington's third-base coach. But one source said the new coach will come from outside the organization.
Listach has a history with the Cubs, managing in the Cubs' Minor League system for four seasons, going 253-221. His best season was in 2008, when he guided Triple-A Iowa to an 83-59 record, and he is still respected by the organization.
Listach was once considered a top managerial prospect, and at age 43, he still could manage sometime in the future. This is an unusual choice as I thought Mike Quade and Jim Hendry would choose someone with previous major league managing experience. But as Ladson's article says, Listach was and still is well-respected by the Cubs organization and he managed a number of current Cubs while in the organization from 2006-2008. He also managed at Iowa for half a season in 2002 after Bruce Kimm was promoted to replace Don Baylor. This also makes it very unlikely that Ryne Sandberg will return to the Cubs organization next year.