PHILADELPHIA -- The Philadelphia 76ers welcomed Joel Embiid back to the floor after missing so much time due to an April 9 appendectomy, but it wasn't enough to even their Round 1 series with the Boston Celtics. The Sixers fell 128-96 as they had a miserable night at home to fall to a locked in Celtics team.

Embiid had 26 points, 10 rebounds, and six assists in his return while Tyrese Maxey had 22 points and and six assists, and Paul George added 16 and four rebounds. Quentin Grimes had 12 points and six assists for Philadelphia off the bench.

Here are the three biggest takeaways following the loss:

Just as it was down the stretch of the Game 3 loss, rebounding was a problem from the jump in Game 4. The Celtics won the rebounding battle 15-5 in the first quarter with six of those 15 coming on the offensive glass. It led to so many second-chance opportunities and Boston capitalized on its chances. Overall, the Celtics won the rebounding battle 51-30 as Philadelphia completely struggled in that department. The Sixers did not grab an offensive rebound until the 6:52 mark of the third quarter.

"Well, they were more aggressive, quicker," said coach Nick Nurse. "They wanted to chase them down more than we did. We just didn't seem like we could get bodies on them. Couldn't run down any long ones. It was a huge problem."

The Sixers turned to Andre Drummond as the backup center in this contest rather than Adem Bona and it led to some issues. Drummond had problems with Boston’s perimeter offensive attack led by Celtics big man Nikola Vucevic in his particular matchup. When considering how well Bona played in Game 3—despite fouling out—one had to believe Nurse would turn back to Bona as the backup. Instead, he went to Drummond and he was a minus-9 in his first 2-minute stint with Boston finding a rhythm in those minutes.

"I mean, I think we got to make a decision on who's going to be the backup to start, and I think our decision was to go with Drum first," Nurse said. "I think he's been playing pretty well in this series, and then we were going to give him the first step. If it went well, just stay with them. Then he got a couple fouls. So then it gave Adem a shot. Then both of them kind of took shots. Drum took a shot to the hip, and Adem took a shot to the wrist and and then we were just trying to kind of survive out there a little bit."

Of course, when Embiid returns, everybody has to adjust. The Sixers had a tough time getting their star backcourt going in this one as the big fella needed to get the ball and get his touches. Maxey only had three shot attempts in the first half and 14 for the game while Edgecombe only took nine shots all night. With the Sixers now facing elimination, they will need to find a way to make sure Maxey and Edgecombe get their looks within the offense. The Celtics deserve credit for the way they’ve defended them, but the two guards are so quick and have the ability to get things going in a hurry. They need to lean on that in Game 5 a bit more.

You mentioned Tyrese’s low shot attempts in the first half, VJ’s low shot attempts for the game. Those two guys both need to make sure they're getting their cracks at it. I think for sure they become kind of our first, second, third options, along with Paul when, when Joel's not in there, but can't go from from like 20 and 25 shots down to as low as it was, especially for VJ. I mean, I think VJ has got to go in there and make some of the plays he's made all year. He’s got to take those things into 15 feet. He's got to take those baseline jumpers. He's got to continue to shoot for 3. Again, I'm saying we got to generate more 3s, and we got to take them, and I think again, we generate a bunch of good ones early again. He gets a couple, again, wide open in the corner. Then we get a little gun shy. We just can't do that. I mean, we just can't. If you miss three in a row, and the next play is for you to take a corner 3, you got to take them, and I think that that also went into it a little bit.

This article originally appeared on Sixers Wire: 3 biggest takeaways for Sixers following Game 4 loss to Celtics