BOSTON -- Philadelphia 76ers star Joel Embiid said "it's going to take awhile" for him to fully round back into form after an extended bout with COVID-19.

Embiid had a second straight rough shooting performance in Wednesday's 88-87 loss to the Boston Celtics.

"I would never use it as an excuse but obviously I think it's going to take me awhile to get back, especially legs and cardio and all that stuff," Embiid said after going 3-for-17 against Boston, making him a combined 7-for-33 across Philadelphia's past two games. "But every single day I got to keep working hard, and keep getting better."

After Embiid scored 43 points in Philadelphia's double-overtime loss to the Minnesota Timberwolves on Saturday in his return, looking like he hadn't missed a day despite nearly three weeks away due to the virus, he has come crashing back to Earth each of the past two games.

He followed up a 4-for-16 dud at home against the Orlando Magic on Monday with his 3-for-17 performance against the Celtics on Wednesday, as Philadelphia's entire team played like it was stuck in mud at that end of the court.

Philadelphia (11-11) shot just 37.1 percent overall and 8-for-31 from 3-point range, including a 3-pointer in the corner by forward Georges Niang with 0.1 seconds to go that was blocked by Celtics center Robert Williams III to secure the victory.

Embiid, however, shouldered the blame for the loss.

"I can't be playing the way I've played these last two games, especially when it comes to shotmaking," Embiid said after finishing with 13 points, 18 rebounds, six assists, two steals and three blocks in 33 minutes. "If teams are going to double me and I'm not going to get easy baskets, I have to create for myself and my teammates, and I've got to make those shots."

Neither team could get anything going all night, with Boston (12-10) eventually getting just enough offense to secure the win in the first game of a brutally tough month of December that features 15 games -- all of which will be against teams that are currently at or above .500.

It is there, with a .500 record, that Philadelphia finds itself just over a quarter of the way through the season -- a sharp dropoff from the 8-2 start that the 76ers enjoyed before losing Embiid for nine games to COVID-19.

He also was shaking his right (shooting) hand throughout the game after it was hit by Enes Freedom in the first quarter, shortly after Freedom was introduced to a rousing ovation by the hometown fans here in his first game after both officially becoming a U.S. citizen and changing his last name from Kanter to Freedom.

It allowed Embiid, however, to say with a big smile, "That's what happens when Freedom gets too much freedom," when he was asked about his hand after the game, later adding that it "hopefully" gets better, and that he felt it the most when he was shooting free throws.

When 76ers coach Doc Rivers was asked what he's seen from Embiid since he came back from the virus and whether it had lingering effects on him, Rivers admitted he wasn't sure what to think.

"Everybody with COVID, I just don't know those answers," Rivers said. "Some guys come back quickly and play pretty well, a lot of guys have played the one great game when they've come back and then gone into a little fog.

"You could tell he's definitely struggling getting going. Yeah, we've just got to keep playing him and letting him play through it."

The Celtics have endured their own example of that with star forward Jaylen Brown, who came back from his own bout with the virus to score 46 points in Boston's season-opening double-overtime loss over the New York Knicks, only to then have some ups-and-downs in his play after that.

Both Embiid and Rivers, however, were not just concerned with Embiid's shooting woes, but Philadelphia's overall offensive malaise. They both spoke about the pace the team is playing with at that end of the court, and want it to be faster.

"We've got to get Joel going," Rivers said. "We get him going, the whole team gets going. That's the number one thing.

"But that's two games in a row I thought the offense was lackluster. Execution is really bad right now. But, again, I'm not concerned by it. We're going to get through it. It's just that we're dropping games while we're getting through it."

In addition to the team's pace, Embiid also pointed out on multiple occasions that he'd like the 76ers, who have been without star point guard Ben Simmons all season as he seeks a trade away from Philadelphia, to have more ball movement.

He added that part of the difficulty in trying to get himself going comes from the fact that he has to do so much work to get himself clean shots.

"The whole season I haven't gotten any easy ones," Embiid said. "It feels like I've got to work for everything. That's why I said we've got to communicate. I've got to let my teammates and my guys know. I probably have to come up with it myself, find ways I can get easy ones.

"It feels like I've had to work for everything, especially it's hard. I get doubled every single possession. If I get doubled, and I'm dribbling the ball and I'm going into a shot, most of the time if I want to get a shot off I've got to go to fadeaways and shooting off the dribble. No team is really allowing me to get to the paint from the time that I put the ball on the floor. They are sending doubles. I've got to be aggressive, I've got to make plays, too. But, most of the time, if it's going to be that way there's a lot of times where I'm going to have to be shooting over double teams."