Marshall, 28, is coming off a year in which he averaged a career high in both points (15.2) and assists (3.3) per game through 47 starts (74 games).
After averaging single-digit points per game in his first four seasons, starting just 46 games, Marshall had his breakthrough season in 2025 when he averaged 13.2 points in 27.8 minutes per game.
The New Jersey native, who shot 51% last season, will be a key piece locked up for the remainder of the decade as the Mavericks continue their rebuild.