If Perez makes the Major League club, he will earn $850,000, plus incentives. He can earn extra money if he makes 20 starts.
Perez, 30, is coming off one of his worst seasons in the big leagues, going 8-11 with a 5.57 ERA in 26 starts for the Royals. He didn't pitch after Aug. 18 because of a sprained left knee.
Those eight wins not only tied for ninth among American League lefties, they matched reliever Jon Rauch's win total. Rauch led the Nationals in victories.
"[Perez] gives us depth to protect us against injuries and also gives us depth so we are not forced to rush our young starters if they're not ready," general manager Jim Bowden said via e-mail. "Will he come back to his form of a few years ago? Not sure, but with [manager] Manny [Acta], [pitching coach] Randy [St. Claire] and [special assistant to the general manager] Jose Rijo -- if there is a chance of bouncing back at his young age -- this is the environment for him to do it in."
Perez will compete for a rotation spot with John Patterson, Shawn Hill, Jason Bergmann, John Lannan and Matt Chico, who was the only starter on the Opening Day roster who never missed a turn because of an injury.
"As Jim puts it, 'You never have enough pitching.' " Acta said. "Perez is a guy with a lot of years of big league experience. That brings up more competition, which is more than welcomed. It's still a fact that we have some guys coming back from injuries. ... He is a left-handed pitcher who still won as many games as any of our guys on our staff at the big league level. He had success before. ... He is a welcome arm over here."
Perez is 66-70 with a 4.47 ERA in 222 games spanning nine big league seasons with the Royals, Dodgers and Braves. His best season was in 2002, when he went 15-10 with a 3.00 ERA in 32 starts for Los Angeles.
This is not the first time Washington had interest in Perez. After Perez went 7-6 with a respectable 3.25 ERA with the Dodgers in 2004, the Nationals targeted him as one of the top free-agent pitchers. But they had no chance to sign him back then, because he was looking for a big payday. He ended up staying with Dodgers and signing a three-year deal.
Bill Ladson is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.