Starting Tristan Thompson and Daniel Theis: a cost benefit analysis

Think back to the Amir Johnson-Jared Sullinger days in Boston. It seems like that was the last time the Celtics started two shooting-challenged bigs at the same time. To start the 2020-21 campaign, Brad Stevens has adjusted his starting lineup a bit to include both Daniel Theis and Tristan Thompson, playing Boston’s most experienced frontcourt players side-by-side against their opponent’s most potent groups.

To a certain extent, Stevens is throwing out his five most-talented players and finding ways to make it work. Kemba Walker is out indefinitely, and upon Kemba’s return, it’s likely that one of Theis or Thompson will return to the second unit.

Motivations aside, it’s the first time in years we’ve seen Stevens roll with two guys who are best being centers. On the offensive end, the fit is awkward, but not unsalvageable. Theis is a career 34.4% 3-point shooter; it’s not like he cannot stand in the corners and make it work flanking a rolling, rebound-chasing athlete like Thompson. The pairing can work, though it limits the number of playmakers, wing defenders and speedy guys on the floor with them.

If Stevens continues to roll out this double big lineup, Boston has to utilize its size and interior advantages. Defensively, the versatility of Thompson to guard on the perimeter for stretches gives them potency in the half-court that other lineups cannot. He did an admirable job against Giannis Antetokounmpo. The combination of he and Marcus Smart gives Boston toughness on that unit that is hard to replicate.

Playing big changes their offensive strategy. Against one-big lineups trotted out by the Milwaukee Bucks and Brooklyn Nets, the offensive glass was available for the C’s to crash. In order to take advantage of the size and strength advantage they have at the 4, crashing the glass is a must.

However, the tradeoff comes in transition, where sending more players to the glass means fewer will be back to protect the rim from quick hit-aheads or speedy attacks. As the NBA has shifted towards more skill and speed at the 4 over the last decade, we’ve seen a decrease in offensive rebounding emphasis. The most elite on the offensive glass, like Thompson, only create a second-chance opportunity 13 percent of the time, snatching roughly one of every eight misses. Remember, these are only misses: if a team shoots 50 percent from the field, and turns it over 10 percent of the time, Thompson only creates four to five extra possessions per game.

Last year, the average NBA team got out in transition about 15 percent of the time and accounted for an average of almost 20 points a game. The reason so many teams have de-emphasized the offensive glass is due to this mathematical tradeoff: it’s better to try and decrease the 20 points than to hunt for what only amounts to a handful extra possessions a game.

In the season opener against the Bucks, Boston gave up eleven transition points in the first six minutes, many of which can be tied to the glass-crashing of the Celtics’ bigs. Many of these come from having a guy like Theis in the corner, having to sprint the length of the court and likely miss making an impact on the defensive end:

Offensive rebounding can keep plays alive and find ways to maximize these two-big lineups... if the defense respects the outside shooting of the other. Theis was standing in the corner throughout the night when paired with Thompson, and it was clear that the Bucks were fine with letting Theis be the one to beat them from the outside. Theis finished the night 2-for-6 from behind the arc.

Antetokounmpo would be the one guarding him, and the reigning Defensive Player of the Year functioned as a free safety, ready to fire down off the corners and block shots at the rim. The secondary value of a free-roaming Giannis: he could help bury Thompson to the baseline, rebound and start the break.

Notice Antetokounmpo ignoring Theis in the clip above which lead to Theis getting lost in transition:

The game against the Brooklyn Nets provided a different challenge offensively, as the Nets switch most actions off-ball. Brooklyn would pass off cutters around DeAndre Jordan, keeping him matched on Thompson when possible. That would mean there were times when Theis was guarded by the much-smaller Kyrie Irving.

The Nets didn’t care. Theis wasn’t a post-up threat to them, and the Celtics didn’t really look to exploit those matchups. If a team is going to go big and not have size advantages they can exploit, what is the point of going big?

Stevens pulled the Theis-Thompson pairing less than three minutes into each half. Whether that’s a sign of things to come remains to be seen. It’s entirely plausible that, with the matchup of a faster, more shooting-heavy Brooklyn and the absence of Robert Williams on Christmas Day, this was a move done to match up with Jarret Allen on the second unit.

The thumping at the hands of the Nets has little to do with these two-big lineups. They haven’t been a disaster, just stylistically challenging. What Stevens’ insistence on playing them might indicate is a lack of trust in the rest of the wing rotation, where there aren’t guys who can handle the responsibility of playing with the first unit and keeping the floor stocked with wings.

We’ll see how much longer these Theis-Thompson minutes continue, and if greater success is possible against different opponents. It’s clear that, until Kemba Walker comes back, these rotations are going to be a patchwork job and require big games from Jayson Tatum and Jaylen Brown to vanquish playoff-caliber foes.