The Nationals plan to scout Strasburg again on Friday, when San Diego State plays Air Force at Tony Gwynn Stadium. Game time is at 9 p.m. ET. Strasburg is 10-0 with 147 strikeouts and 15 walks for San Diego State this season.
"He is our top choice right now, but what if he gets hurt? We can't say today that Strasburg will definitely be the guy. A lot could happen between now and then," the source said.
Published reports indicated the Nationals will not be scared off by the price tag -- believed to be $50 million-plus -- for the right-hander. But the source expects the negotiations between the Nationals and Strasburg's advisor, Scott Boras, to go down to the wire.
If he is drafted and signed by the Nationals, Strasburg will go straight to the Minor Leagues.
The Nationals also have not ruled out drafting right-hander Aaron Crow for the second year in a row. Last year, Washington could not reach an agreement with Crow, their first-round selection in the 2008 First-Year Player Draft, by midnight ET on Aug. 15. Money turned out to be the sticking point.
The Nationals are going to watch Crow pitch for the Fort Worth Cats of the American Association of Independent Professional Baseball on Monday.
By not signing Crow last year, the Nationals will get the No. 10 pick in this year's Draft as compensation.
Acting general manager Mike Rizzo and team president Stan Kasten did not return several phone messages on Monday, but Rizzo said on Saturday the Nationals are close to deciding which players they want to select for the entire draft.
"We are well on our way with the draft preparation. It is right around the corner and we are starting to finalize our targets for 1,  and beyond. That's kind of the mode we are in right now," Rizzo said. "We are putting the final touches to our list. We are going to take the best player available.
If it's a pitcher, so be it. You know  is a terrific pick. It's a high pick. We are hoping to get an impact player.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.