The Nationals used their third starting shortstop in three games this season, moving Felipe Lopez over from second base for Wednesday's series finale against the Marlins. Opening-day shortstop Cristian Guzman left after straining his left hamstring, then was put on the 15-day disabled list Tuesday. Josh Wilson started the second game, but now Lopez -- who switched from shortstop to second base this spring -- will fill in while Guzman is sidelined.