There really isn't a clear-cut choice for the No. 1 fantasy defense/special teams (DST) entering the 2021 NFL season. If anything, that just means you may be able to wait even longer than usual to get one in your fantasy draft.
Consider that the Los Angeles Rams, who finished first in fantasy points (Athlon scoring) in 2020 are ranked fourth below. Yes, Aaron Donald is still around to wreak havoc up front and Jalen Ramsey anchors the secondary, but he's lost two running mates in cornerback Troy Hill and safety John Johnson III (both signed with Cleveland in free agency), and coordinator Brandon Staley is now the Chargers' head coach. That's enough uncertainty to drop the Rams a few spots.
So who is No. 1? That distinction would go to the Steelers. Pass rusher Bud Dupree is no longer around, and the secondary will look a little different, but Pittsburgh still has at least one playmaker on each level. This is a defense that has shown a knack for getting to the quarterback and creating turnovers for the last several years, and that's probably the key thing to look for when it comes to picking your DST.
But the gap between the Steelers and the Rams is not that big, and don't forget about two DSTs in between them – Buccaneers and Ravens. Any of these teams figure to be a solid choice on draft day, even if none of them end up as the No. 1 fantasy DST when all is said and done.