Mattingly didn't rule out the possibility of a trade before Sunday's deadline, saying the front office has floated "a few different names, but not a lot."
Earlier this month, general manager Ned Colletti said he hoped to add a reliever and left-handed power bat, but has since said nearly every player put on waivers has been claimed and blocked from being dealt.
When rosters expand Monday, the Dodgers will call up a small group of Minor Leaguers. Outfielder Joc (30/30) Pederson will be one.
"You could assume that," Mattingly said. "One guy that deserves to get called up."
Other callups likely include catcher Tim Federowicz, reliever Yimi Garcia, infielders Erisbel Arruebarrena and Alex Guerrero.
"Guys always provide something," Mattingly said. "It might be in a blowout to give guys some innings off. It won't be a tryout camp, but there could be guys that are very important to what we do. We're not going to throw guys in just to give them at-bats."
Mattingly also said reliever Chris Perez, out since Aug. 4 with bone spurs in his right ankle, will be activated Monday. Left-hander Paco Rodriguez is the only other player currently on the disabled list with a chance of returning this season, but he's still not recovered from a strained Teres Major muscle.
Ken Gurnick is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.