WASHINGTON -- Infielder Mark DeRosa and left-hander John Lannan have been taken off the Nationals' playoff roster, according to a baseball source. The Nats have not made an official announcement, which is expected on Saturday.

Manager Davey Johnson said he planned to use four starters during the postseason, and Lannan is the club's fifth starter. The veteran spent most of the season in the Minors Leagues, and he went 4-1 with a 4.13 ERA for the Nationals, mostly as replacement for Stephen Strasburg in the rotation during the month of September after Strasburg was shut down for the season. Strasburg was on an innings limit after having Tommy John surgery in late 2010.

Wild Card vs. Nationals

DeRosa missed a lot of time because of injuries this past season, but that didn't stop him from becoming a great teacher to the younger players such as second baseman Danny Espinosa and shortstop Ian Desmond. In fact, outfielder Roger Bernadina credits DeRosa for his productive season. It was DeRosa who told Bernadina to start using a lighter bat. DeRosa was also a person who kept the clubhouse loose.

A favorite of Johnson's, DeRosa played in 48 games and went 16-for-85 (.188) with six RBIs. DeRosa will most likely travel with the Nats to St. Louis to be a veteran clubhouse presence for a ballclub short on players with postseason experience.