PHILADELPHIA — About an hour before the 76ers faced the Celtics on Thursday night, Philadelphia announced that its star center, Joel Embiid, would need surgery to repair a torn ligament in his left ring finger, and that he would be sidelined indefinitely.

The Celtics, meanwhile, have navigated through the first half of this season dealing with one malady after another, and they had surged toward the top of the East anyway. Now they were mostly whole again, and they had a chance to capitalize on a rival missing its superstar.

Instead, Boston coughed up a 15-point lead and stumbled to a 109-98 loss, its season-high third in a row.


After falling to the Wizards and Spurs in recent days, coach Brad Stevens acknowledged that some warning signs had emerged. The Celtics were not playing as hard as they should, and that concerned him.

Following this defeat, though, his tone was more upbeat.

Enes Kanter goes hard to the basket Thursday against the Sixers.
Enes Kanter goes hard to the basket Thursday against the Sixers.Matt Slocum/Associated Press

“I mean, the league is hard,” he said. “You can feel pretty good about yourself and one week later not so hot. These guys just went through it over here last week. But inevitably, there’s another game and if we play like we did tonight, clean some things up and play with a little bit more pop, I like what we’re becoming. I’m just not as discouraged as I’ve been the last couple days.”

Celtics point guard Kemba Walker missed three games with an illness and was then ejected in the third quarter of Wednesday’s loss to the Spurs for directing profanity at an official. So Thursday was his first real chance to be back, and he had several All-Star spurts while pouring in 26 points. Marcus Smart, whose 3-point shooting has regressed this season, hit 5 of 7 and scored a season-high 24 points, perhaps an encouraging sign.


But those two received very little help. Jaylen Brown’s first minor offensive rut of the season continued for another night, as he made just 2 of 12 shots and had three turnovers. Jayson Tatum and Gordon Hayward combined to go 8 for 24.

“Some easy shots I normally make, I didn’t,” Brown said. “Threes, layups, for the last two or three games they went in and out, for whatever reason. I’m going to keep working. That’s it. Just continue to shoot them with confidence. They’re going to go in. I’m sure of that.”

Because of all the injuries and illnesses, Boston’s top players have been on the court together infrequently this season. And games like this one are reminders that this group that is filled with athletic, slashing wings is still figuring out how to be at its best together.

“It’s tough,” Smart said, “because you got guys who are already in their rhythm and you got guys trying to come back and get into the rhythm. It’s going to take awhile for us. But it’s nothing to hold our heads down about.”

Backup point guard Brad Wanamaker was an essential part of Boston’s fast start and had appeared in every game this season. But he has struggled recently and did not play Thursday. Stevens said that was partly due to the size problems that the 76ers pose, and that Smart was shooting so well, but it was another example of how the coach continues to tinker with player groupings as the season nears the midway point.


The 76ers, meanwhile, will now have to figure out how to move forward in the congested top half of the Eastern Conference standings without Embiid, who is expected to be reevaluated in about two weeks.

Thursday’s game was a promising start. Josh Richardson led Philadelphia with 29 points, and the 76ers made 48.9 percent of their shots and 40.7 percent of their 3-pointers. Philadelphia held the Celtics to their fifth-lowest point total of the season despite the absence of its defensive anchor.

Marcus Smart finished with 24 points in the loss.
Marcus Smart finished with 24 points in the loss.Matt Slocum/Associated Press

“When he’s not around we have to be on edge,” 76ers center Al Horford said, “and it’s like, ‘Don’t get beat off the dribble.’ You’ve got to be there and we don’t have that rim protector like Joel is. We have to get creative, and that’s what we did tonight and we found a way.”

The Celtics held a 51-36 lead with five minutes left in the second quarter, but then they had a scoring drought that stretched for more than four minutes, as Philadelphia went on a 12-0 run and pulled within 55-48 at halftime.

Boston was still clinging to an 82-79 lead near the start of the fourth quarter, but it made just 1 of 7 3-pointers and attempted just one foul shot in the period, and the 76ers pulled away behind 14 points from Richardson.

“They just were too comfortable,” Brown said. “For whatever reason, guys are a little too comfortable playing against us. We’ve got to watch the film, get back in the lab. All is not lost.”


Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him on Twitter @adamhimmelsbach.