Assuming Doucoure can defend a specific player better than Harper or Yeboah.
Bigs pick up fouls. This is where we're tight on the roster - bodies to preserve our bigs against the whistle.
In our last regular season game, Doorson/Johnson/Carter had a combined 12 fouls in 42 game minutes. Two games before that, Johnson/Carter had 9 fouls across 29 game minutes. There will be minutes at the 5 spot because of foul trouble, and when Pike won't want to throw a 6-6 guy against a 6-11 guy for extended time.
Even if Doucoure just gets spot minutes, I still expect him to average 6+ min/game for the season. Without him, we have just 2 centers and 2 PFs (who also spend time at the SF spot) - and there's a lot of contact in the paint in the B1G. With Doucoure on the roster, we shouldn't be forced into a 2015-16 situation with DJ Foreman playing center and Laurent at PF. We have a third center, and I'm pretty sure he'll see time.