Why the Celtics Will Win the NBA Finals

The NBA Playoffs have begun and there are several teams that can win the championship. As of April 21, there are 6 teams with at least a 5% chance of winning the championship according to 538.com’s NBA predictions. After years of shortcomings in the playoffs and a slow start to tis year’s season, I think the Celtics will win the NBA Championship.

The Celtics may have started the season 23-24 at the 10 seed in the East through mid-January, but they ended the regular season 28-7 behind the best defense in the league, led by Defensive Player of the Year Marcus Smart. Offensively, they have been trending up and they might be the most balanced team in the playoffs. Here are some more reasons I think the Celtics are the favorite to win the NBA Finals.

(Getty Images)

Offense

While the Celtics may be led by their defense, their offense is still one of the league’s best. The Celtics had the 7th best offensive rating during the regular season, and they pride themselves on being very balanced offensively. The Celtics rank in the top half of the NBA in each of the four factors (eFG%, TOV%, ORB%, FT/FGA) on offense.

The Celtics offense is one of the most balanced in the NBA. They are efficient on shots at the rim, pull-up field goals, and contested three point attempts. The Celtics have shot 69.6% inside the restricted area this season, the 3rd best mark in the league. Their rim efficiency has been led by the efforts of cut and roll big men like Robert Williams and Daniel Theis in addition to star players Jayson Tatum and Jaylen Brown. Williams has a field goal percentage of 81.4% off cuts, making him a versatile player on offense by capitalizing when the defense pays too much attention to the ball handler. Theis has been an effective rollman on pick and rolls, having the ability to roll to the rim or pop out for a 3-point attempt while scoring 1.42 points per possessions on these plays.

If defenses are stopping the Celtics from getting to the rim, they can operate in the mid-range to create their own shots. Jayson Tatum and Jaylen Brown specialize in creating their own shot off the dribble, with a 45.5% and 47.4% eFG% respectively on over 7.5 pull up field goals per 100 possessions each. One of the Celtics’ most under-the-radar players is Payton Pritchard. Pritchard has been a great offensive spark off the bench, showing the ability to create his own shot and serve as a good spot up shooter. Pritchard averages 1.073 points per shot on pull-up field goal attempts and 1.256 points per shot on catch and shoot attempts, ranking in the 94th and 90th percentile of the NBA, respectively. When the Celtics need a bucket in a tough situation, at least of one Tatum, Brown, and Pritchard should come through. All three of them shoot well on contested 3-point attempts, making at least 34% of these shots. While I’m talking about 3-point shooting, the Celtics offense has only one player (Robert Williams III) that won’t shoot 3’s. Among the Celtics’ other 8 playoff rotation players, 4 are very good floor spacers (Jaylen Brown, Jayson Tatum, Payton Pritchard, and Grant Williams) and 4 are willing to shoot but aren’t as efficient (Al Horford, Marcus Smart, Derrick White, and Daniel Theis).

The theme with the Celtics offensively seems to be balance. The Celtics have a balanced offensive attack, a balanced mix of players that are good at the rim, and, a balanced mix of players who can create their own shot. Another element of the Celtics balance is their balance of players that can initiate the offense. Using box creation (a stat developed by Ben Taylor that estimates the number of open shots created per 100 possessions), the Celtics have 5 players who create over 5 shots per 100 possessions. These players are Tatum, Brown, Pritchard, Marcus Smart, and Derrick White. What’s even more impressive is that all of them except Smart are good at limiting turnovers. This is a strength because it decreases the variance of the Celtics offense. With multiple shot creators, it is very unlikely that all of them are playing poorly, ensuring that the Celtics offense doesn’t sputter. In contrast, the Hawks, Mavericks, and Nuggets are more heliocentric, meaning the offense flows primarily through one player. A result of this is that these teams struggle more in the playoffs because defenses have an easier time game-planning to stop just one player as opposed to five. Having just one high usage shot creator also makes a team’s offense less consistent because if the main creator is having a bad game, the offense cannot operate.

Finally, I want to show the Celtics’ recent offensive trends. The Celtics offense has been improving over the course of the entire season, increasing the points per 100 possession after each month. Using SABER, which adjusts for location and strength of opponent on the game level, we can see the Celtics’ offensive trend line. They have had just two really bad games (-10 or lower game offensive SABER) since Mid-February and have outplayed the opponent consistently, meaning their offense is better than it seems and improving.

Y-Axis should say “Offensive Game SABER”

Defense

Defense has been where the Celtics have thrived all season long. Their defensive rating is ranked 1st in the NBA by forcing the lowest opponent eFG%. The Celtics defensive success starts with their defense at the rim. They force the 3rd lowest shooting percentage within 6 feet of the hoop, behind only the Cavaliers and the Spurs. Not only are the Celtics great at forcing misses at the rim, but they succeed in preventing offenses from even getting to the rim. Shots close to the hoop are still the most valuable despite what people may think about 3-pointers, so preventing teams from taking shots at the rim is among defenses’ highest concerns.

Photo by Nathaniel S. Butler/NBAE via Getty Images

Marcus Smart may have won Defensive Player of the Year, but I would argue that he wasn’t even the most important player for the Celtics’ defense. He may have forced lots of turnovers (more on that later), but he did not have nearly as large an effect on shot defense as Robert Williams or Al Horford. Williams and Horford have defended the rim as well as anyone this season, with opponents shooting just 51.9% (on 6.6 shots per 100) against Robert Williams and 54.7% (on 8.1 shots per 100) against Al Horford within 6 feet of the rim. They are both also two of the best shot blockers in the NBA, with Robert Williams having the 3rd best block percentage (6.8%) and Al Horford possessing the 10th best (4.2%), according to Basketball Reference. The Celtics only major weak link in their inside defense is Daniel Theis, who has allowed 63.1% of shots within 6 feet of the rim on 10.9 shots per 100 possessions. As Robert Williams returns for the Celtics from his injury, I believe it would be in the Celtics’ best interest to limit Theis’s minutes in favor of Williams, as Williams is a lot better defensively while still being a threat down low on offense. The only skill in Theis’s favor over Williams is shooting.

The Celtics having a good rim defense is obviously helpful, but what may be even more impactful is the fact that they allow very few shots at the rim. They allow the 5th lowest frequency of shots at the rim, the 5th lowest frequency of dunks, and the 6th lowest frequency of layups. As mentioned earlier, shots at the rim have the highest expected value, so the Celtics are forcing opponents to take lower value shots, decreasing their expected output. However, the Celtics defense isn’t like the Bucks, who notoriously have allowed few shots at the rim at the expense of allowing a lot more three point attempts. Rather, the Celtics are forcing their opponents to take more mid-range shots. This makes their defense even better as mid-range shots have the lowest expected value of almost any shot.

Now, you may think that the Celtics’ defensive tendency to allow a lot of mid-range shots may hurt them when they play good playoff teams who have several players that can efficiently attack the mid-range, like Kyrie Irving and Kevin Durant of the Nets or Chris Paul and Devin Booker of the Suns. However, the Celtics not only allow lots of mid-range shots (again, probably one of the worst shots in basketball), but they also defend the mid-range at the 2nd best rate, allowing just 39.2% of mid-range field goal attempts to be converted. Mid-range defense is certainly less consistent than rim defense or even mid-range offense, but 7 of the Celtics’ 9 rotational players are in the 76th percentile or better in mid-range defense. Even if mid-range defense isn’t consistent, there is no way all of them have defended mid-range shots well just from dumb luck. Al Horford, Jaylen Brown, Daniel Theis, Robert Williams, Derrick White, Grant Williams, and Payton Pritchard all allow less than a 39% mid-range field goal percentage. Further evidence of the Celtics’ ability to force bad shots is that just 46.5% of their opponents’ 2-point attempts and 78.9% of opponents’ 3-point attempts are assisted, the lowest and 3rd lowest rates in the league, respectively. For reference, the average 2-point assist rate is 51.4% and the average 3-point assist rate is 82.5%.

You may be wondering where Marcus Smart factors into the Celtics’ defense. The Defensive Player of the Year winner must factor into the Celtics’ astounding defense somehow, right? Well, the answer is yes. But his major effect on the game doesn’t come from his ability in contesting shots (although he is still very good at this). Instead, his impact in limiting offenses stems from his ability to be a pest and force lots of turnovers and low quality possessions by deflecting the ball. Marcus Smart records 3.2 deflections per 36 minutes, ranking in the 90th percentile of the NBA. This is huge for a Celtics team that gets the 4th fewest deflections in the NBA, their one defensive weakness. By deflecting the ball, Marcus Smart is able to either take a possession away from the offense or put the offense in a scramble mode where they have to recover with fewer time on the shot clock, leading to worse quality shots. This trait will be important for the Celtics moving forward, especially as they face offenses that tend to turn the ball over rarely, like the Suns, 76ers, and Bucks.

Other Reasons the Celtics are the Best Team

There are two other reasons why I believe the Celtics are the title favorites, but they don’t necessarily fit into the category of offense or defense. The first is playoff experience. The Celtics’ two leading players may be on the younger side, but that doesn’t mean they don’t have playoff experience. The Celtics’ core of Jaylen Brown, Jayson Tatum, and Marcus Smart has played in the Playoffs every year since 2018 (advancing as far as the Conference Finals in 2018 and 2020), making this year their 5th playoff run together. In addition, Al Horford has played in the Playoffs 13 different seasons. As a result, the Celtics have 4 rotational players with at least 1700 playoff minutes, which is the most of any team in this year’s Playoffs. Even when including their less experience players and taking the weighted average of career playoff minutes (where the weight is regular season minutes per game), the Celtics have the 7th most experienced playoff roster, just behind Miami and Phoenix, both of which have made the Finals in the past two years. Even though the Celtics are young, playoff experience is not an issue.

The other reason I think the Celtics are the favorites is that they have several lineups that have absolutely dominated during the regular season. The Celtics two most frequently used lineups have outscored opponents by at least 24 points per 100 possessions. Their most used lineup during the regular season was Tatum-Brown-Smart-Horford-R.Williams. This lineup had a net rating of +24.6 and was efficient offensively and defensively. This makes sense, seeing as on offense the Celtics have their two best players on the court and defensively it contains their three best defenders without any liabilities. Their next most used lineup, which is the same as the previous one but switches in Grant Williams for Al Horford, actually outscores opponents by 31.0 points per 100 possessions as it improves their offense by adding one of the league’s best catch and shoot players to complement the playmaking of Brown and Tatum without a significant defensive dip. As of this writing, the Celtics are already up 3-0 on the Nets and I actually think they will be even better in their next series against the Bucks since they will be able to use these lethal lineups that can suffocate teams offensively and defensively.

SABER Ratings + Probabilities

Now that I have detailed why I think the Celtics are the title favorites, here are the team ratings and title chances according to my NBA SABER rankings, which ranks teams based on net efficiency and adjusts for factors like recency, location, strength of opponent, player absences, and defensive 3-point luck. In order to have a more accurate ranking of teams for the NBA Playoffs, I included an adjustment for playoff experience, giving a boost to the teams possessing the most experience while lowering the ratings of teams with less experience based on a linear regression.

My model also has the Celtics as the title favorites, followed by the Warriors and the Suns. This agrees with other predictive tools, including betting markets and 538’s NBA Predictions. The Celtics should be the NBA title favorite because of their upward trending and balanced offense, tendency to force bad shots on defense, and effective lineup combinations.


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