Marshall didn't participate in Friday's practice, Mike Curtis of The Dallas Morning News reports.
Marshall recently returned from a four-game absence due to an illness, posting 19 points (7-11 FG, 2-4 3Pt, 3-4 FT), four rebounds, two assists and one steal across 29 minutes in Tuesday's 118-104 loss to the Thunder. It's unclear if he's still battling the ailment or dealing with a new injury. Either way, Marshall's availability for Sunday's game versus the Warriors is now in doubt.