Yeah, I've really come around to the idea of Cauley-Stein starting. It seems like a terrible idea for a team with playoff aspirations to have a rookie in the starting lineup but unless Karl wants to flip-flop lineups a lot to have Gay starting at PF with Cuz at C or Boogie starting at PF with Koufos at C depending on matchups then I don't see a great alternative.
Gay will struggle against a lot of big/post up PFs. So against Griffin, Aldridge, Randolph, Sullinger, Nene, Gasol, Millsap and Anthony Davis it'd be a tough thing to start Rudy at the four.
Likewise against George (if he really does play a lot of PF for IND), Love, Nowitzki, Green, Faried, Morris, Parker, Patterson, Ilyasova, etc Cousins is going to have a very tough time chasing guys around the perimeter. And while he'll have a huge advantage in the post against all of those guys, having Koufos at C means a more clogged paint and likely fewer post up touches because of it.
Cauley-Stein has the length to defend tall/power players and the quickness to guard perimeter oriented PFs. I expect him to struggle against talented veterans like Blake and LMA and the Brow but he's the best defensive option IMO. And perhaps more importantly we saw that if Koufos starts our second unit is very weak on the boards. Cousins can cover for WCS not being a strong rebounder and Koufos can help the fact that Acy also isn't great on the glass (or aid Gay if he shifts to the 4) giving more balance.
I'm a big Koufos fan and I think he should get a ton of minutes but without too much of a kneejerk reaction based on one preseason game I have to say I'm not a huge fan of starting DeMarcus and Kosta together.
Cauley-Stein still wouldn't play huge minutes or likely be in at the end of games (likely logging the fewest minutes among the starters) but he's a very good option to start games and feel out the pace and style of play before making substitutions.
My $0.02