One possible solution to this quandary (not having a top 4 talent available to you when you have pick #4) is to find a team that does think there's a player worthy of that pick, and engineer a trade with them for the #4 pick.
There are 31 other team's scouting departments and talent evaluators who will have different grades on players than what the Patriots have, so there might be a buyer for that pick.
The best case would be having multiple buyers, especially if they're QB needy teams, of which there are many this year. If Ward, Carter, and Hunter go 1-2-3 in some order, there may be a team that's willing to move up a few spots to grab Sanders, especially if they think there's a team above them that will snare him first.