Players with at least 10 years of major league service, including five consecutive years with their current club, cannot be traded without their consent. Guzman made his debut in the majors with Minnesota in 1999 and joined the Nationals in 2005, their first season in D.C.
Nationals manager Jim Riggleman said the team will not make an announcement about Guzman until Saturday. The Washington Post reported that the Nats will get two Double A starting pitchers -- Ryan Tatusko and Tanner Roark -- in return.
Last night, the Nats traded All-Star closer Matt Capps, who recorded his 26th save of the season yesterday, to the Minnesota Twins for two prospects, including catcher Wilson Ramos, who General Manager Mike Rizzo said is ready to catch every day in the majors right now.
The trade deadline is 4 p.m. Saturday, and first baseman Adam Dunn is rumored to be bound for the Chicago White Sox.