The team is also without reliever Javy Guerra, who is on the bereavement list to visit his hospitalized father in Mexico.
Mattingly said he would see how things go after Jansen and Belisario threw on Sunday before making a decision whether he would use them.
"We'll see how they feel today and then make decisions accordingly," said Mattingly, who added both relievers have pitched three days in a row before.
Jansen threw 26 pitches on Saturday -- including 11 on a hard-fought strikeout of Cameron Maybin -- while Belisario threw 18. Belisario allowed a run to score in the eighth to cut the Dodgers' lead in half, while Jansen was saddled with a blown save after giving up two runs on an odd steal of home in the ninth.
Each reliever threw a scoreless inning on Friday with Belisario throwing 10 pitches and Jansen throwing 15.
While the back end of the bullpen has been worked lately, the rest of the team's relievers haven't pitched since before the All-Star break.