Harvin is a risky play against Skins and so is A Brown with the possibility of Big Ben out. Also, Felix Jones may not play or be limited. Sammy Morris has been picke up a lot already. Personally, I would replace Jones with Spiller and replace A. Brown with Kevin Smith. SD defense can be stout at times, but Smith is electric. SD gives up aroudn 5 catches per game to running backs and Smith is heavily involved in the pass attack.
So, I would leave Harvin starting, but just know it's a gamble. Continue to monitor Felix Jones. If he doesn't practice at all today or tomorrow then I would roll with Spiller. I know DEN defense has been pretty good, but spiller can also catch passes out of the backfield well, so that's a big plus if you're in a PPR league