WEST PALM BEACH, Fla. -- Washington Nationals reliever Will Harris has a blood clot in his right arm and is leaving spring training camp to be examined by a specialist, manager Dave Martinez said Friday.

"I don't know much about what's going to happen here. But for me, when somebody mentions something like that, it's kind of a scary deal," Martinez said. "Until we know more about it, then I got to assume that he's going to not start with us this season."

Opening Day is April 1.

"He felt weird his last outing," Martinez said. "So we kind of backed off a little bit, got an MRI, and in the arm was a little small blood clot."

The 36-year-old Harris last pitched in an exhibition game on March 9, throwing one scoreless inning against the Houston Astros. The right-hander appeared in a B game Saturday.

"Medically, I don't know the extent of what that is. But I know it's something that is serious," Martinez said. "We need to take care of it. Take care of it as soon as possible. And I feel for Will, 'cause I know he was just working his tail off to help us this year."

Harris, then with Houston, gave up a tiebreaking two-run homer to Washington's Howie Kendrick in the seventh inning of World Series Game 7 two years ago, a game the Nationals won 6-2 for their first title.

He has been expected to be a part of a formidable back end of the bullpen along with Brad Hand and Daniel Hudson for Washington, which finished last season tied for last in the NL East.

"He's pretty upbeat considering what's going on," Martinez said. "Hopefully we'll know more sooner than later, and then we can determine what's going to happen."