The team was hoping that Olsen could pitch a full season, but he is having left shoulder surgery to repair a small tear in his labrum. Right now, only left-hander John Lannan is expected to pitch a full season.
Acting general manager Mike Rizzo admitted that some of the plans have to be changed, but would not reveal what they were.
"We have to make adjustments," Rizzo said. "Innings have to be made up from somewhere with a cautious approach with the Zimmermanns of the world. Our young starters have to make some adjustments."
By the end of August and early September, the Nationals could call up right-handers Collin Balester, Marco Estrada and Shairon Martis to fill some of those innings.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.