6:36pm: Rizzo told reporters, including Zuckerman, that the Nationals' "Plan B" after missing out on Buehrle could involve Oswalt or other free agents and trade candidates. He has talked to the Athletics about Gio Gonzalez.
5:20pm: The Nationals had hoped to sign Mark Buehrle, but their offer to the left-hander fell short in both years and average annual value, tweets Adam Kilgore of the Washington Post. With Buehrle off the board, the Nats will switch their focus to Roy Oswalt, says Kilgore.
Kilgore reported in November that Oswalt was Washington's "Plan B" if the club couldn't land Buehrle. GM Mike Rizzo told reporters (including Mark Zuckerman) today that the Nationals aren't interested in other free agent pitchers, though Zuckerman clarifies that was before news of Buehrle's agreement broke (Twitter link). Oswalt is said to be seeking a three-year commitment.