The lasting image of Derrick White in last year’s playoffs was a timid playmaker and hesitant shooter.

When he did shoot, White went 36.4% from the floor and canned fewer than a third of his 3-pointers. The player the Celtics had acquired at the deadline, an offensive connector and defensive hound, folded like his team did in the Finals.

Nowadays, it’s hard to remember that player. White emerged as a consistent two-way force over the regular season and cemented that impression with a 24-point performance in Game 1 against Atlanta.  Before the Celtics tipped off in Game 2, coach Joe Mazzulla explained the difference he’s seen in White’s game between then and now.

“I think he’s just more confident, more comfortable, has more of an identity,” Mazzulla said. “I think any time you join a team late, especially a team that’s been together for a long time with high expectations, you’re just trying to figure out how you can have an impact and where you can. … He can handle for us, he can play off the ball, and he’s really gotten used to our defensive schemes, as far as our switching and how we match up and kind of what the coverages are based out of those matchups.

“He has an effect off ball, on ball, at the rim at times. And so I just think he has a clear-cut identity.”

In Game 1, White went 7-of-13 from the floor, including a 4-of-7 showing from distance. He added seven assists and five rebounds, plus two blocks. He also helped corral Atlanta guard Trae Young, who was limited to 16 points over a poor shooting performance. In the regular season, White averaged 12.3 points, three rebounds and six assists over three games versus the Hawks.