First, the Celtics have zero players over 6'11", or even that tall. Second, since it was my post that set this off, my principal point wasn't the height issue, it was a positional issue. We have two 5s, Horford and Baynes. We don't have anyone else who has experience at that position. Morris, Hayward, Tatum, and Brown are all small for the 4 and are not 5s, even in a small ball unit. Theis was a 5 in Europe but is undersized. He might be able to play the modern NBA 5. Semi and Yabu both have the potential strength to play a small ball 5, but they are both rookies and neither is proven. The odds either can actually pull off a role that basically only Draymond Green has demonstrated the capacity to play at their size is not good.
In other words, even accepting the realities of the modern NBA, we remain very thin at the 5. It's not an issue of lack of height, and I shouldn't have made it seem that way, although height is a factor. It's an issue of us lacking a guy I'm comfortable with as a third 5. In other words, I actually would feel a lot more comfortable with our big depth if we had Tyler Zeller at the back of the roster. There are still several players like that out there, though, so it may be that Ainge feels no real pressure to add one just yet. He may want to see what Theis, Yabu, and Semi bring to the table before making a move, and that's fine.
But, without someone else who looks like a rotation player at the 5, starting Baynes and Horford together seems like an unlikely option for our roster construction.