"He's swung the bat well," Mattingly said before Wednesday's game against the D-backs. "This is really where he's earned to be."
In a corresponding roster move, the Dodgers optioned infielder Justin Sellers to Triple-A. Sellers, the club's Opening Day shorststop, was hitting .191 with one homer and two RBIs in 26 games.
"We felt like we had plenty of infielders, and really from the standpoint of looking at it more like it's just a little bit better hitting bench, where you can use some guys to hit," Mattingly said.
The manager said Federowicz would back up A.J. Ellis, and veteran Ramon Hernandez would be the No. 3 catcher and an emergency first baseman.
With three catchers, the Dodgers can use either Ellis or Federowicz as a pinch-hitter when the other starts and keep Hernandez on the bench in an emergency role. Hernandez is 1-for-22 (.045) in eight games since being acquired from the Rockies via trade on April 6.
"It's part of the reason for Fed," Mattingly said. "We've always felt like Fed was the guy coming and Fed was the guy who was going to get the at-bats. Ramon gives us that third guy that can play first and really allows us to use all of our people."
Austin Laymance is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.