Pierce is a SF, but he could play SG. In the 2008 Finals, he stepped up and guarded the best SG in the league.
Daniels can play both too. He is quick enough to stay with must SG's. He may not be strong enough to handle SF's in the post, but he definitely had the length.
Players like Ray and Rip work through various screens. Even Wade and Kobe have trouble staying with them, and they are regarded as two of the best defenders at the position.
After game #10, I'd be surprised if we saw a lot of Wafer, besides the occasional shooter lineup, or because of foul trouble or an injury. But he should see ~15 MPG to start the season.