The Heat now lead the series 2-1 after Boston's 117-106 triumph Saturday in Orlando, Fla. The Celtics can even the series if they win Game 4 Wednesday at the ESPN Wide World of Sports Complex inside Walt Disney World Resort.
"I'm looking forward to the next game," Brown told reporters. "I think we all are. So, we got to keep our minds locked in and engaged.
"The game doesn't start on Wednesday. The game starts now. So, getting ready and getting prepared for the next one is just as important."
Boston led by as many as 20 points in Saturday's win, while the Heat never held a lead. Brown had 26 points, seven rebounds, five assists and three steals in the victory. Tatum had 25 points, 14 rebounds and eight assists.
The Celtics outscored the Heat 31-22 in the first quarter. Boston outscored Miami 32-28 in the second frame for a 63-50 lead at the break.
The Heat cut the lead to five points with 55 seconds remaining before Marcus Smart made eight consecutive free throws down the stretch to secure the victory.
"Our whole team was aggressive," Celtics coach Brad Stevens said. "Our whole team played with the right mentality.
"And most importantly responded to their good runs and tough shots really well and then pushed leads out."
Heat center Bam Adebayo had 27 points, 16 rebounds, three steals and two blocks in the loss. Tyler Herro scored 22 points and had four assists off the bench for the Heat. Jimmy Butler had 17 points, eight rebounds and three assists for the Heat.
Smart had 20 points, six assists and four rebounds for Boston. Kemba Walker had 21 points, six rebounds and two assists in the win.
"Boston came out with great force in this game and you do have to credit them for that," Heat coach Erik Spoelstra said. "They sustained it for the better majority of the game."
The Heat battle the Celtics in Game 4 at 8:30 p.m. EDT Wednesday in Orlando.