No. 2 Boston Celtics vs. No. 3 Philadelphia 76ers

Game 1: 76ers at Celtics, 7:30 p.m. ET Monday (TNT)
Game 2: 76ers at Celtics, 8 p.m. ET Wednesday (TNT)
Game 3: Celtics at 76ers, 7:30 p.m. ET May 5 (ESPN)
Game 4: Celtics at 76ers, 3:30 p.m. ET May 7 (ESPN)
*Game 5: 76ers at Celtics, May 9 (TNT)
*Game 6: Celtics at 76ers, May 11 (ESPN)
*Game 7: 76ers at Celtics, May 14
* if necessary

BetMGM series odds: No. 2 Celtics -350, No. 3 76ers +260

Other conference semifinals previews:
Denver Nuggets vs. Phoenix Suns: Can Nuggets slow down Suns’ offense to kick off Round 2?

The Eastern Conference’s second-seeded Boston Celtics and third-seeded Philadelphia 76ers meet in the second round of the 2023 NBA playoffs. Boston has won the last two playoff meetings by a total of 8-1.

3 keys to the series

What the heck do the Celtics do against Joel Embiid?

In case you have not watched the NBA for the past three years, 76ers center Joel Embiid is 7 feet, 280 pounds and somehow plays bigger than that. He is the two-time returning MVP runner-up and will almost certainly win the award this season, when his 33.1 points per game led the NBA for a second straight season, and he added 10.2 rebounds, 4.2 assists and 2.7 combined blocks and steals in 34.6 minutes a night.

He also has never been able to remain healthy throughout two rounds of the playoffs. Multiple surgeries on his right foot cost him the first two years of his career. Embiid suffered a second-round gentleman's sweep at the hands of the Celtics in his 2018 playoff debut, when a fractured orbital bone forced him to wear a mask. He has gutted through the playoffs ever since — on a sore left knee in 2019, an ankle injury in 2020 (when Boston fully swept Philadelphia), a torn right meniscus in 2021 and another orbital fracture last year.

Now, Embiid is playing on a sprained LCL in his right knee, which cost him the finale of a first-round sweep of the Brooklyn Nets. Had the Atlanta Hawks not extended Boston's first-round series to six games, Embiid likely would not have played a Saturday Game 1 of these Eastern Conference semifinals, Sixers coach Doc Rivers told reporters on Thursday. With the opener now scheduled for Monday, Rivers said, "I'm just going to wait" on a status update for Embiid, whose injury has kept him from practicing with the team for a week.

None of this is encouraging for the 76ers, whose matchup with All-Star Celtics wings Jayson Tatum and Jaylen Brown has been a challenge. Boston trusts Al Horford — and has started to trust Grant Williams — to defend Embiid. While the Sixers star has remained productive against both over the past two seasons (104 points on 53.2% shooting in 58 minutes, per the NBA's tracking data), his team has struggled in those situations, scoring just 1.01 points per possession — the equivalent of an average pre-3-point era offense.

Interestingly, Boston's double-big combination of Horford and Robert Williams III — a pairing that transformed the Celtics into an elite defensive team the past two seasons — has not been so effective against Philadelphia. With both of them on the court against Embiid, the Sixers are +18 in 46 minutes in the last two years. With just one of them on the court opposite Embiid, Philly is -35 in 127 minutes, largely because Boston's offense has scored an astounding 1.27 points per possession in those scenarios.

The Celtics have been most effective trusting single coverage in isolation against Embiid, and then showing a second defender when he goes to work in the post. In a small sample size of 27 double-teams on Embiid's 84 post-ups against Boston over the past two years, the Sixers are scoring just 0.85 points per chance. The Celtics can trust their past success against Embiid, hope the historical effectiveness of their double-big lineups finally translates to this matchup and benefit in both lineups if injuries further limit him.

This is more than most teams can rely upon against Embiid, whose status as a perennial MVP candidate means he can shred every scouting report by performing at his regular season peak. You should be able to tell where Embiid stands in this series by watching him late in games, where over the last six seasons his 27.8 points (on 50/33/82 shooting splits) in 32.3 minutes per game during the regular season have dipped to 21.9 points (on 44/24/90 shooting splits) per 32 minutes of fourth quarters and overtime in the playoffs.

What the heck do the Sixers do against Jayson Tatum and Jaylen Brown?

Here are the Sixers who have spent more than five minutes defending Tatum this season, per the NBA's tracking data: De'Anthony Melton, Tobias Harris, P.J. Tucker, James Harden and Embiid. In 50 minutes matched up against those players, Tatum scored 83 points on 46/36/60 shooting splits — pretty good, but here's the catch: The Celtics have scored an astronomical 1.33 points per possession in that sample size.

It does not help that whichever wing is not defending Tatum must guard Brown. The All-NBA candidate rested the last regular season game the Celtics played against the 76ers — Philadelphia's only win in four tries — and suffered a facial fracture in their second meeting. In the two games Brown did finish against the Sixers this season, he totaled 62 points on 53/38/88 shooting splits. His assignment usually falls on Harris, who has given up a little more than a point per minute to Brown in that function over the past three years.

Tucker is 37 years old and had trouble staying in front of Tatum a year ago, when the veteran drew the assignment for the Miami Heat in the Eastern Conference finals. Tatum amassed 43 points (on 48/50/100 shooting splits) and 12 assists opposite Tucker in 40 minutes of that series, per the tracking data. Melton and Jalen McDaniels are capable defenders, but neither can be counted upon to elevate the offense to a level that makes their defensive impact against two elite wings a winning calculation in a seven-game set.

Herein lies the problem. The Sixers want to play Harden and Tyrese Maxey as often as possible. Tatum and Brown can hunt each of their best two guards, and if both can hunt either, well, that is a math problem even Philadelphia general manager Daryl Morey cannot solve without some outlying offense from his own team.

Who are the fourth- through 10th-best players in this series?

Prime Harden could do a lot to produce that outlying offense if he, too, were not battling physical ailments. He missed six of Philadelphia's last 11 regular season games with a sore left Achilles tendon. A strained tendon in his right foot cost him a month earlier in the season, and both of his hamstrings have hindered his performances in each of the previous two postseasons. This is the nature of 33-year-olds not in top shape.

(This is where we remind you Harden went to Las Vegas between series and allegedly slapped someone.)

Harden was ineffective in the first round from everywhere but 3, where he finished 14 of 33 (42.4%) in four games. He made four of his 17 field-goal attempts (23.5%) in the restricted area, seven of his 30 attempts (23.3%) in the paint and got to the free-throw line a total of 11 times in the series — a far cry from when he got to the rim at will and took 11 free throws per game as a top-three MVP candidate from 2016-20.

Harden's struggles open the door for any number of Celtics to supplant him as the fourth-best player in any game of this series. Derrick White was Boston's difference-maker against the Hawks, averaging 17.3 points on 56/46/91 shooting splits. In 31 minutes with either Harden or Maxey defending him during the regular season, White scored 32 points on 13-for-21 shooting (4 of 9 from deep), according to the tracking data.

Marcus Smart, Malcolm Brogdon, Horford and either Williams all have the capability of being the fourth-most impactful player behind Embiid, Tatum and Brown in any one game, so long as Harden is not healthy.

It will be on Maxey and Harris to ensure the Celtics do not have something like six of the best eight players in the series. They were spectacular against Brooklyn, combining for 42.1 points per game on 52/52/87 shooting splits in the first round. Both excelled in their roles during the regular season, too, but that is the kind of outlying effort that could swing this series against historical precedent. Even performing at their regular season level would go a long toward tightening the margins if Embiid and Harden also hold up, but sustaining your averages against Boston's waves of talented guards and wings is easier said than done.