Martis will start the year on the major league roster, but Zimmermann will begin in the minor leagues before his first start, against the Florida Marlins on April 19.
The Nationals also put outfielder Wily Mo Pena on waivers Saturday and reassigned infielder Jose Castillo and outfielder Corey Patterson, a former Oriole, to minor league camp.
Catcher Javier Valentin also was reassigned but opted to become a free agent. Pitcher Collin Balester was reassigned to Triple-A Syracuse.
The Nationals will carry only four starters to begin the season because of the spacing of three days off April 5, 9 and 14.
The Nationals released Odalis Perez on Feb. 23 and Shawn Hill on March 18.
Indians:: General manager Mark Shapiro would not comment on reports he told 2008 American League Cy Young Award winner Cliff Lee he wouldn't negotiate a contract extension for the left-hander. The Plain Dealer in Cleveland reported Friday that Shapiro had told Lee the Indians wouldn't negotiate an extension because of the nation's uncertain economic conditions. Lee will be paid $5.75 million this season, and the Indians hold a club option at $9 million for 2010.
Et cetera:: In his first start since agreeing to a four-year, $15.5 million contract, Gavin Floyd (Mount St. Joseph) shut out the Dodgers over six innings, scattering seven hits while striking out seven in the White Sox's 6-1 exhibition win in Glendale, Ariz. ... Angels ace John Lackey received a cortisone shot in his right elbow in an attempt to relieve the pain in his arm, and it's uncertain when he will pitch again. ... Catcher Ronny Paulino was traded for the second time in 24 hours, and he's now with Florida. The Giants sent Paulino to the Marlins for minor league right-hander Hector Correa. The deal was announced Saturday after Paulino was traded Friday to the Giants from the Phillies for left-handed pitcher Jack Taschner. ... Shortstop Derek Jeter bruised a knuckle on his left pinkie in the Yankees' exhibition against the Braves in Lake Buena Vista, Fla., but he remained in the game and the team said Jeter is fine.