The Boston Celtics suffered another blow before the start of the new season. The team's main forward Jaylen Brown injured his left hamstring in the last preseason game and is currently listed as day-to-day observation.

Brown's availability for next Wednesday's regular season opener against the Philadelphia 76ers remains uncertain. Boston Celtics head coach Joe Mazzulla said Brown participated in all activities except scrimmage during Friday's practice and is making steady progress, but the team will carefully evaluate his condition.

"I haven't spoken to him after practice yet," Mazzella said. "I want him to be in top form every day and we'll take it one step at a time."

Brown suffered the injury during Wednesday's preseason game against the Toronto Raptors. He left the game midway through the first quarter after feeling tightness in his left hamstring and did not return. The Boston Celtics narrowly won the game 110-108, but Brown's injury overshadowed the team's victory.

The Boston Celtics are facing pressure to rebuild their team this season. Core player Jayson Tatum will be sidelined for a long time due to a ruptured Achilles tendon, and they lost four key rotation players over the summer: Jrue Holiday, Kristaps Porzingis, Al Horford, and Luke Kornet.

In this lineup, Brown is regarded as the team's offensive pillar and spiritual core. If Brown cannot return in time, the Boston Celtics may face a severe test at the start of the season.