Not sure what your issue is. I saw a couple of 5 pf games, but I wouldn't say that he is getting 5 pfs EVERY game. Plus in each of those games he has like 35+ minutes. Even a guy with average stamina is still going to tire if you play him that much. And most of his fouls must be coming towards the end of the game, otherwise he wouldn't get that many minutes to begin with.
Finally - he is only 20 so his experience can't be that high. And yes - his outside d and low shot blocking can be contributors. I noticed that in one of the games that he got 5 pfs that your opponent was playing run and gun. The centre took a few 3 pt shots and probably a few others were jump shots.
Anyhow, I suggest watching your games live. Then you'll see where your team's fouls are coming from. Even a bad team outside d can contribute to non-shooting fouls.
Run of the Mill Canadian Manager