Probably because the only big guys we have now are a 6'8" freshman and two 6'7" wing guys who don't exactly have the bodies yet to defend the paint at the A10 level.
Nobody is saying Relvao was a stud, but like others said he could give you a handful of minutes, especially during games where foul trouble becomes a factor. We won't miss him every game, but there will be a handful of games this year when not having another big body option will hurt us.
I'm not sold on Calixte yet. It's not like he had major offers out of high school or an eye popping stat line (he averaged 14 points per game - meh). Maybe others got some inside info that he is tearing it up at practice - I don't know... but putting all of our eggs in his basket scares the crap out of me. I hope he can defend A10 bigs without getting in foul trouble, but that's a lot to ask of a freshman!
It’s definitely going to take some creativity to help Calixste up front against bigs in the A10 or even non conference. But that said I think Wilson will help around the 4, and Mar helping at the wing may alleviate as well. The three of them are going to have to step in and be ready to go.
You may have to have the deny the post dare to shoot strategy more often then not if Calixste gets in trouble.