"G is really frustrated with the way things are going," Mattingly said. "I just don't want that to boil over into worse. So we'll give him a day here. He will play [Tuesday]. We'll talk about the last day [of the series] when we get there."
Mattingly said Stanton isn't hurt, but noted the sore right side that caused him to miss the final week of May has impacted his swing a bit.
For the season, Stanton's slash line is .192/.299/.415 with 12 home runs and 29 RBIs.
Getting Monday off was a mental break, as well as a day to work on things in practice without testing them in a game situation.
"Decompressing a little bit and not trying to take that out there," Mattingly said. "It's been a little bit of a balance because of the side [soreness]. When he first came back, he couldn't take all the swings that he wanted, and still keep playing. He had to balance that a little bit. I think that's a little bit of a gray area, where you want to keep him on the field, but you also have to work enough to get sharp again."
As Stanton aims to snap out of his slump, Ichiro continues his trek toward a couple of memorable milestones. The 42-year-old went 3-for-4 Monday and has 4,259 hits as a professional, one shy of Pete Rose's MLB record.
Ichiro has 2,977 big league hits, 23 shy of 3,000. He also collected 1,278 in nine seasons playing in Japan.
"You have to admit, getting him in there is enticing right now, because of what he is able to bring to the table for us," Mattingly said. "But I think it's two-fold, from what we talked about with G, to help him get on track. But to have Ichy to play, and have him as a leadoff guy, and hopefully spark us."
Joe Frisaro has covered the Marlins for MLB.com since 2002. He writes a blog, called The Fish Pond. Follow him on Twitter @JoeFrisaro and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.