Have we seen Theis on Giannis? Theis was out during the playoffs last year and I don't have a good memory of Theis guarding Giannis during this regular season. I know he hasn't been good for a while but, physically, he seems like he'd be as well suited at tangling with Giannis as anyone.
In the 1st Milwaukee game this year, where the C's won, Brown and Theis were out and Semi started and played 22 minutes, mostly all on Giannis.
In the second meeting, Horford, Morris and Baynes we're out so Semi started but if I remember right Brown, Smart and Hayward spent most of the night on Giannis while Semi and Theis played against Lopez and Maker. C's lost by 13.
In the last meeting this year, Bucks won by a point, the Celtics were shorthanded again with no Hayward or Baynes. Semi played 12 minutes, Theis 6 minutes and neither did much of anything. It was mostly Morris and Brown on Giannis, if I remember correctly.
So, the Celtics will be down Smart in the series, but I think Stevens will go with Morris, Hayward and Semi on Giannis with Brown denying Middleton.