Estrada was given anti-inflammatories, and he will begin throwing again once the symptoms clear. There is no timetable set for his return.
Estrada played in 17 games, and he went 7-for-39 (.179) before going on the disabled list Friday for the second time this season.
Estrada, who spent time on the DL earlier this season, has never recovered from offseason elbow surgery, and he said a few weeks ago that he shouldn't have went full speed when Spring Training started.
In other news, first baseman Nick Johnson has a right wrist tendon strain. He's listed as day-to-day. It is not known how Johnson hurt the wrist, but the Nats sent out an e-mail to reporters about the injury.
Johnson played on Tuesday against the Mets, and he went 0-for-3 with a walk.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.