Lilly last pitched for the Dodgers on Apr. 29.
The left-handed pitcher was released by the Pirates on May 8 after putting up an 11.85 ERA in five appearances, including four starts.
To make room on the 40-man roster for Van Slyke, pitcher Chad Billingsley was transferred to the 60-day disabled list.
Accepting Nick Punto and Juan Uribe as temporary starters, the current Dodgers bench of Skip Schumaker, Luis Cruz, Justin Sellers, Herrera, and Ramon Hernandez has hit a combined 30 major league home runs since the beginning of the 2011 season, and 1
The Dodgers could gain some much needed roster flexibility at a time when they absolutely need it with one simple move, one with minimal cost.
Gordon his .314 with a .397 on-base percentage with 19 runs scored and 14 stolen bases in 25 games for Triple-A Albuquerque this season.
Laffey is 25-29 with a 4.45 ERA in 153 games, including 68 starts, in parts of seven major league seasons with five teams.
Guerra will be the 19th player to throw a pitch for the Dodgers this season. The only three pitchers left on the 40-man roster to not pitch for the Dodgers in 2013 are Scott Elbert (on the disabled list), Steve Ames, and Chris Withrow.
Fife has right shoulder bursitis and is on the disabled list retroactive to Apr. 22. Magill, who was added to the 40-man roster in November, will make his major league debut on Saturday night against the Brewers.
Lilly will be the eighth starting pitcher used by the Dodgers in 2013, in their 20th game. In 2012, the Dodgers didn't use an eighth starter until their 108th game.
The left-handed pitcher began the season on the disabled list retroactive to Mar. 28, and has made two rehabilitation starts in the minor leagues.
Greinke's spot in the rotation doesn't come up again until Tuesday against the Padres at Dodger Stadium.
Sending down the catcher creates a roster spot that will be filled on Wednesday with the activation of Chad Billingsley from the 15-day disabled list.
Barring an injury, Federowicz will be optioned to Triple-A Albuquerque before Wednesday's game against the Padres.