Boston still has questions to answer over its final roster spot.

Does Xavier Tillman leapfrog Luke Kornet? Will Boston fill its 15th roster spot? Let's explore some options.

Xavier Tillman has agreed to sign a two-year, fully guaranteed contract with the Boston Celtics. Adam Himmelsbach of the Boston Globe has reported the deal is for the veteran minimum.

I was wrong on this one.

I came into the offseason believing Brad Stevens would keep one of Luke Kornet or Tillman. When Kristaps Porzingis is healthy, the Celtics have a deep rotation of bigs. One or two of them are going to get buried on the bench. Tillman struggled to crack the rotation after joining in February. He did have some big minutes in the NBA Finals, though.

So, while I’m pleased Tillman is sticking around, I have some questions.

1. When Porzingis is healthy, what does the big man rotation look like? Assuming Joe Mazzulla primarily sticks to a single-big rotation, the Celtics hierarchy will likely look like this:

   1. Porzingis

   2. Horford

   3. Kornet or Tillman

   4. The loser of the Kornet/Tillman battle

   5. Queta

Tillman and Horford can slide to the four in double-big scenarios, which can better use the team’s depth. However, for most of the minutes when Porzingis is in the rotation, two guys are glued to the bench. I struggle to see why Tillman would re-sign if he didn’t believe he could leapfrog Kornet.

2. Does Kornet’s 1-year deal vs. Tillman’s 2-year deal indicate who will be the third-string big? Boston had bird rights for both guys. They could have inked Kornet to a longer contract if both parties had been open to the idea. Could giving him a shorter stint with the team be an indication? Maybe I’m reading too much into it, but…

3. While it’s almost become cliche at this point, Tillman does project as a potential long-term successor to Al Horford. They play a similar style of basketball; they are both versatile defenders and sneakily strong for their size. They both excel as do-it-all bigs impacting the game outside of the box score. If Tillman can improve his perimeter jumper and add a mid-range pull-up, floater, or push-shot out of the short roll, he will be a valuable backup.

   1. Horford has one year left on his current contract. While there’s no guarantee, he will likely walk off into the sunset after the upcoming season. He’s a champion now. He could be a two-time champion by the time his deal expires. Tillman would then slot into the void and plug the gap.

   2. The upcoming season could be Tillman’s chance to work as Horford’s understudy. Learn his routine. Figure out how he’s so successful at using angles to his advantage on the defensive end. And get advice on how to expand his shooting range onto the perimeter with a reliable consistency.

Stevens hasn’t committed much money to keep either Tillman or Kornet in Boston. He has, however, made it a point to retain as much of the championship core as possible. There will undoubtedly be a battle for minutes in that third-string big-man spot, and I doubt we will get an answer coming out of training camp.

Kornet and Tillman bring different skill sets to the table. There will be a time and place for both of them to stake their claim for the postseason. Still, I found the decision interesting and enjoyed the mental gymnastics I performed when working through the string of questions that arose in my overactive basketball brain.

Still, with Tillman locked up, the Celtics have one roster spot left. Over the next few days, we will look at some potential options with that final roster spot, or whether i’s wise to leave it open.

It’s a reach, but it just might work…