The Celtics lineups without Al Horford and Aron Baynes

Aron Baynes’ injury on Wednesday night put the Boston Celtics in a rather difficult position. The team has been without center Al Horford for the last six games, and the 32-year-old will miss number seven when the Milwaukee Bucks come to town on tonight. For a team that can offer arguably the most depth in the NBA, Boston suddenly finds themselves unfortunately thin in their front court.

Baynes is expected to miss about 4-6 weeks after having surgery on Thursday to put a pin in his injured finger. The Australian big man has been an integral piece for the Celtics so far this season, especially during the absence of Horford. If you didn’t know what Baynes brings to the table, Wednesday night’s loss highlighted all of his strong-suits in the worst ways possible. After exiting the game just two minutes into the first quarter, Boston was crushed on the glass by the Phoenix Suns and rookie DeAndre Ayton. The Celtics were out-rebounded 56-37, and allowed the Suns to grab 21 offensive rebounds. Ayton would ultimately finish with 23 points and 18 rebounds (8 offensive).

So who do the Celtics have left in the big man rotation? Second year center Daniel Theis and rookie Robert Williams.

Both players will see increased time with absences from Baynes and Horford, which we saw on Wednesday night with less than optimistic results. Williams saw 24 minutes of action in the loss, while Theis was on the floor for 21. Both players are reliable big men, but they present different skill sets.

Baynes is someone who will come in, crash the glass, and protect the rim. Williams certainly has rim protection covered, as he currently ranks first in the NBA with 6.4 blocks per 36 minutes (minimum of 100 minutes played). As the Boston Globe’s Adam Himmelsbach pointed out, the next closest player in that category is Hassan Whiteside at 3.9. Those blocks oftentimes draw him away from the basket and/or with his back to the basket. Blocks can provide second chance opportunities, which means Williams’ teammates will have to help crash the boards. Kyrie Irving made a point of this following Wednesday night’s loss.

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“Us as guards, when we’re missing guys, we have to help Rob rebound as well,” said Irving. “He’s contesting and trying to go for every block. Our weak side, and crashing in, and helping him out is just as important as him going for the rebound. That’s part of being on the team, we all have to cover each other.”

Williams has had stretches of PT during some Gino Time throughout the Celtics 8-game winning streak, and due to the rash of injuries, the small samples bear out some promising numbers. Time Lord has only played more than six minutes with two different lineups. The first five-man combination is with Terry Rozier, Semi Ojeleye, Brad Wanamaker, and Guerschon Yabusele. That lineup has a net rating of -68.1, but is clearly one of the team’s garbage-time fivesomes. The second group is one that Williams could definitely find himself in over the next few weeks. A combination of Kyrie Irving, Gordon Hayward, Marcus Smart, Jayson Tatum, and Williams has a net rating of 26.3 in 10 minutes played. Don’t be surprised if this five-man group sees some time together over the next couple games. Replacing Hayward with Marcus Morris in this lineup presents another interesting combo with a net rating of 40. Williams is a dangerous lob threat alongside good ball-handlers, so any time on the floor with Irving, Rozier, and/or Hayward creates a solid opportunity for the 21-year-old.

A look at lineup combinations will quickly show that Boston rarely plays without Horford or Baynes, but the responsibility of filling in at the five won’t fall solely on the rookie’s shoulders. Williams has become a fan favorite over the last couple of weeks, but it might be Daniel Theis who could be the more solid replacement at center in December and January.

Out of the Celtics’ top 15 five-man lineup combinations sorted by minutes, there are only two that don’t include either of the currently-injured big men. For example, the lineup of Smart, Morris, Rozier, Tatum, and Theis has played 35 minutes together in six games. That’s the most out of any five-man group without Baynes and/or Horford. They have a net rating 23.6, which ranks 7th out of lineups that have played ten or more minutes. With this group having significantly more time together on the floor, their rating should be more accurate than some of the other combinations with little to PT. The next closest lineup has played 18 minutes over 3 games, and, including said lineup, there are only four other combinations that have played more than 15 minutes together.

Of those four, the group of Gordon Hayward, Semi Ojeleye, Smart, Rozier, and Theis has the best offensive rating, defensive rating, and net rating (124.2, 52.9, and 71.3, respectively). If you replace Smart and Ojeleye with Jaylen Brown and Morris in that same lineup, the numbers fall, but not drastically. Inserting Brown and Morris sends the offensive rating to 122.5 and the defensive rating to 63.2 for a net rating of 59.3, which is good for second in all of those categories for the lineups that played 15-plus minutes.

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The probable starting five over the next few weeks is Irving, Smart, Morris, Tatum, and Theis. This combination has played 18 minutes together over three games, with a net rating of 39.4, which is the fourth-best net rating for lineup with Theis (minimum 10 minutes). Another notable Theis lineup? Hayward, Irving, Morris, Smart, and Theis. In 10 minutes played, this combo has a net rating of 62.4. Both these lineups seem to provide a good mix of length along the perimeter, with guys who can help out Theis on glass.

Theis represents a more multi-dimensional game in comparison to Williams at this point in their careers. RWIII is a great rim protector and lob threat in the pick-and-roll, but still presents a limited, raw game outside of that. Theis shines when he gets the ball around 18-to-20 feet out in a non-PR set. He’s shooting 38.5% from behind the arc and has the ability to attack close outs.

From less than 10 feet, Theis is shooting an effective 69.4%. The German big man has developed a decent catch and shoot game over the last year, forcing defenders to keep an eye on him along the perimeter. Three pointers account for 25.5% of his catch and shoot opportunities, in a similar fashion to the way Baynes works away from the basket. This isn’t something Theis should be relying on by any means, but it’s another dimension that can create opportunity for Brad Stevens on the offensive end, especially off high-ball screens.

Theis’ game gives the Celtics some decent flexibility, which is why he’ll likely start in Big Al’s spot. Timelord will get his minutes too, but Theis can work away from the basket, help spacing, and be a reliable passer in Boston’s offense as the closest reproduction of Horford. Time will tell what lineups we see Brad Stevens go with in the short term, but it’s pretty clear that Theis and Williams will see the largest spikes in playing time. With Giannis Antetokounmpo coming into TD Garden tonight, the Celtics thin front court will once again be put to the test.