"He tweaked his back, we think, very minor," manager Dan Jennings said. "But we need him to test it so we can see exactly where he is. So he could be here in the next day or two."
The Marlins haven't ruled out Morse being in the lineup for either Saturday's or Sunday's games against the Cubs at Wrigley Field.
Morse has been on the disabled list since May 26 with a right index finger sprain. He got off to a rough start this season, batting .211 with two home runs and 10 RBIs.
Since he's been out, Justin Bour has received a bulk of the playing time at first. Bour's progression, including home runs in three straight games against the Giants this week, has the Marlins weighing whether to use Morse at positions other than first base.
Morse played 84 games in left field with the Giants last year, and he has 237 total games in that position. He's also played 179 games in right field in his career, as well as nine at third.
"When we put this roster together this winter, one of the things we talked about was the versatility of players and the willingness to have guys who can play first, play third, play left," Jennings said. "You've got guys who can move around, and you get the best bats or best matchups in the lineup on any given day. We will look at that. That's what our intentions are, and we'll see how we'll proceed."