WALTHAM, Mass. – Celtics swingman Jaylen Brown is doubtful for Monday's opening game of the Eastern Conference semifinal series vs. the 76ers with a hamstring injury, according to coach Brad Stevens.

Brown suffered the injury late in the second quarter of Boston's 112-96 win over the Milwaukee Bucks in Game 7 of their first-round series on Saturday.

"The last email I saw was that he still has some soreness, didn't try to do anything that I know of running-wise today," Stevens said after the Celtics had a film session at their practice facility on Sunday. "He did have some testing and that looked good, thankfully."

But apparently, not good enough.

"He is doubtful for (Monday), but I guess he could play," Stevens said. "It looks like it could be something that allows him to play as the series goes on."

This is yet another blow to an injury-plagued Celtics team.

The Celtics lost five-time all-star Kyrie Irving to season-ending knee surgery in late March. Prized free-agent acquisition Gordon Hayward only played one game before he suffered a season-ending fracture dislocation of his left ankle.  Reserve forward Daniel Theis is also out following knee surgery.

The 6-foot-7 Brown was Boston's second-leading scorer in the Milwaukee series, averaging 17.9 points per game — and that was after scoring just two points on Saturday.

Brown, 21, is one of the NBA's most improved players. He averaged 6.6 points last season as a rookie and this season averaged 14.5 points.

Stevens said he didn't know who would replace Brown in the starting lineup if he isn't able to go. The Celtics coach mentioned either Marcus Morris or Marcus Smart as possibilities, but wouldn't make a decision until Monday.

Allen happy for the city, to a point

Celtics assistant coach Jerome Allen grew up in Philadelphia. He was a high school standout at Episcopal Academy and a college star at Penn before eventually becoming head coach there.

He has mixed emotions about facing the 76ers in the semifinal, which begins Monday in Boston.

On one hand, Allen naturally wants to end the Sixers' season. On the other, he has appreciated from afar what they have accomplished in earning their first playoff berth since 2012.

"I am excited for everybody in the city, excited for the Philadelphia fans, I was a fan growing up as a kid," Allen said after Saturday's Game 7 win. "Now I work for the Celtics and we will try as a staff to come up with a successful game plan."

Stopping the Sixers in transition

Few players are as versatile as Celtics power forward-center Al Horford. He might be one of the only players capable of guarding both Ben Simmons and Joel Embiid.

Horford says the Sixers pose plenty of other problems, especially on the fast break.

"Simmons and Embiid obviously are two great players and they are a great team in transition," Horford said. "I think they are the best team in transition and they make you pay and it presents a whole different challenge going against them."

One positive for the Celtics: In Game 7, Milwaukee had zero fast-break points.