Smart has been sidelined since Jan. 30, when he suffered a calf strain against the Los Angeles Lakers, but has returned to the team's travel party and taken part in "light on-court activities," per Wojnarowski.
He's averaging 13.1 points, 6.1 assists and 1.8 steals, all career highs, through 17 games.
"Marcus is essential to our team, man—he's been great," guard Jaylen Brown told reporters when Smart went down. "Whether the numbers show it or not, Marcus has been a leader on this team; he's been somebody that has been looking to get guys the ball in the right spots, including me."
The 26-year-old, a two-time All-Defensive selection, had an increased role for Boston at the start of the season, since star point guard Kemba Walker was recovering from a stem-cell procedure in his knee.
Now that Walker has returned to the lineup, the Celtics have more offensive firepower, but Payton Pritchard, Jeff Teague and Javonte Green will have to continue to fill the void as the team awaits the return of its heart and soul on defense.