It really depends what lineups and style Pop wants to play IMO. With his traditional 2 bigs he was a SF and couldn't ideally be anything else, but those lineups were relatively slow anyways... for example see his highlights above against the Grizzlies. He had no problem with Vince Carter.
However, in small ball he should be a 4, which is what we saw him play the last 2 games against GSW and he had 20 points, 7 rebounds, 2 asssists and 4 steals. It really depends what style Pop wants.
We don't know if Pau starts or what.