Isaiah Thomas addresses the media for the first time since the death of his sister and thanks everyone from the staff at the TD Garden to his teammates and coaches for being supportive throughout the week. (1:11)

CHICAGO -- Celtics guard Isaiah Thomas said his mind is not fully focused on basketball as he grieves the loss of his sister, and he's feeding off the support of his teammates during Boston's first-round series against the Bulls.

"Mentally and emotionally, I'm not here, so I just feed off what the guys give me," Thomas said while addressing reporters for the first time since his younger sister, Chyna, died in a single-vehicle accident on April 15, a day before the series began.

Thomas scored 33 points Sunday and helped Boston post a 104-95 triumph over the Bulls in Game 4. The series is tied 2-2.

Thomas was joined by teammate Gerald Green and Thomas' two sons, James and Jaiden, at the podium after Sunday's win but requested that he be asked no questions about the loss of his sister. He did occasionally reference the emotional toll he's endured over the past eight days.

"[My teammates] give me a lot of confidence. I can't do it without those guys. They believe in me," Thomas said. "Being here is what makes me, I guess, sane. It makes me feel somewhat normal through these tough times."

Thomas, who looked emotionally exhausted while the Celtics dropped the first two games of the series in Boston, has appeared more himself the past two games. His trademark smile has returned, especially when he's dazzling on the court as he did throughout much of Sunday's win.

After the Bulls rallied from a 20-point deficit to pull ahead midway through the third quarter, Thomas scored or assisted on all 16 points the Celtics scored over the final 5:12 of the third as they retook the lead.

His teammates have noticed an obvious change in his demeanor, and it's lightened the mood in the Celtics' locker room that previously had a bit of a cloud hovering over it.

"Even [in Game 3] I felt [Thomas] was great. He was more clearheaded, and [Sunday] it was back to seeing what we've seen all year," said Al Horford. "He just took over the game and it was big for us."

Celtics coach Brad Stevens said it's still "unfathomable" to him the way Thomas has played given what he's going through off the court.

"I can't believe it," said Stevens. "I tried to say that earlier this week. But what he's been through and the day-to-day, it's been unfathomable the way that he's performed on the court. It's been really incredible. And it didn't go our way in Boston, but the guys were resilient enough to come back and tie this up. But we have a long way to go. But what he has done has been remarkable."

Thomas appreciates the support his basketball family has shown.

"[The Celtics have] been really important," said Thomas. "I mean, they've been everything. This organization is the best organization there is, from the people who work in the Garden to the players, the coaches, everybody who's a part of the Celtics. They've been supportive. The whole world has, really, so I can't say enough about that."