Remember back in May when Jared Sullinger's father, Satch, said that the Boston Celtics "kind of promised" they were going to acquire a center this summer? Fans salivated about the possibility of acquiring a player like Omer Asik or Larry Sanders, but instead the Celtics served up Tyler Zeller.

Sullinger has started losing weight, so he is keeping his end of the bargain, but have the Celtics? Even though Sanders is still available, it's likely that Boston's apparent "rim protection acquisition promise" begins and ends with Zeller.

Even though Zeller is not the huge splash fans were hoping for, the 24-year-old center should provide some much needed rim protection for the Celtics this season. He isn't much of a shot blocker, but he uses his quick feet and proper technique to consistently disturb shots.

"Tyler will be the first to tell you that he's not going to block shots like Mutombo," said coach Brad Stevens when asked about the potential of playing Zeller alongside Sullinger. "He's more of a position defender. He's a strong guy, he's an agile guy, he can move his feet laterally, but he's not necessarily a huge shot blocker at the rim."

Despite those positive attributes, Zeller has never been thought of as a rim protector in the NBA since Cleveland's perimeter defenders were sieves the past two seasons. Kyrie Irving and Dion Waiters are extraordinarily talented offensive players, but their defense leaves a lot to be desired.

When guards are constantly allowing dribble penetration there is really only so much a big man can do, which was a major problem for the Cavaliers. With strong perimeter defenders like Avery Bradley, Marcus Smart, Rajon Rondo and Jeff Green, Zeller could have a career year defending the paint.

Zeller has displayed intelligence when it comes to positioning, rotations, and in help situations, despite being surrounded by open-the-floodgates defenders in Cleveland. This is crucially important when it comes to playing true team defense, which is why his presence should automatically help Boston this season.

Player S OPA/36 Contest % Adj. Saved/36 Blocks/Fouls Blocks/36 Vitor Faverani 2.48 49% 7.18 0.36 2.0 Tyler Zeller 1.49 47% 6.19 0.28 1.3 Jared Sullinger 0.12 43% 4.82 0.20 0.9 Joel Anthony -0.09 50% 4.61 0.71 2.3 Kelly Olynyk -1.30 34% 3.40 0.12 0.7 Brandon Bass -2.09 24% 2.61 0.37 1.1

The chart above uses rim protection data from Seth Partnow, which was derived from SportVU. Sorted by "S OPA/36," Partnow says this statistic details "how many more (or less) points per 36 minutes does this player prevent with their rim protection than an average NBA big man." For a full description of the stats used, click here.

To put it very simply, the collective numbers essentially suggest that Brandon Bass, Kelly Olynyk, and Jared Sullinger are poor rim protectors. Vitor Faverani actually performed quite well last year, saving 7.18 points per 36 minutes pace adjusted. However, he was inconsistent, fouled too much (5.5 fouls per 36 minutes), and is coming off a meniscus tear. For a player who already has displayed only average mobility, there's no guarantee that he gets back to the same level.

Faverani started Boston's first six games last year, but it wasn't just for his offense. Brad Stevens was looking to have a long near 7-footer that could protect the rim, at least at an adequate level. Faverani was the only option at the time. They later acquired Joel Anthony, who played well in limited minutes, but at 32-years-old he is not in the team's long term plans.

That brings us right back to Zeller, who is the strongest candidate to start the season at center. If the Celtics stick to a similar plan, then Zeller is absolutely the best choice. Even though his numbers don't pop off the chart, his points saved per 36 pace adjusted of 6.19 ranks near proven back-up rim protectors like Ed Davis, Samuel Dalembert, and Nazr Mohammed.

In all five clips above, the Cavaliers defended the pick-and-roll using "ice," which is the technique the Celtics (and most teams) used last season. (Read parts one, two, and three of my pick-and-roll series for explanations on these defensive techniques.) In each play Zeller displayed quick and controlled feet, which is especially important when defending with ice. Since he's trying to force the opponent into long two-pointers or threes, he must successfully prevent the ball handler from penetrating and then close-out to contest the shot.

Zeller's ceiling is limited due to his lack of shot blocking ability, but that doesn't mean that he can't make an impact on the team this season, especially since his aptitude for protecting the paint is higher than any other player on the roster. The Boston Celtics may have come up short in acquiring a top-notch rim protector, but they fulfilled their promise to Satch and Jared by acquiring Tyler Zeller.

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