Here is the quote from DC.COM:
Backup Corners: Anyone not named Terence Newman, Anthony Henry or Aaron Glenn still has some work to do. Jacques Reeves and Nate Jones have been solid special teams players in past but are getting pushed by Quincy Butler, Joey Thomas and rookie Alan Ball.
"When you can't tell which one is good enough, maybe none of them are," Phillips said. "I hope that somebody steps up. I like what some of the things they're doing, certainly. But I don't have a good feeling that we've got four corners or five corners that can really play."
In this quote, that comment was made in reference to backup CBs.
The four or five corners which WP made reference to are Reeves, Jones, Butler, Thomas and Ball.
It is a clear references to five corners fighting for roster spots to backup starting CBs.