There are always more sleepers on my list than I have roster spots. Even in a deeper league, say a 16-teamer with six bench spots instead of a "standard" 12-team format, there's always someone else I can look at and think, "I see the upside".
In that spirit, here's some skill players who don't have a lot of buzz heading into the season and probably aren't rostered in your league, but who could be just one big performance away from being waiver wire darlings. If you do happen to have a spot or two available after moving guys to IR, and all the obvious Dede Westbrooks and James Conners are already gone, these guys could provide a windfall:
Running Backs
Ito Smith, Falcons - He didn't do much in the preseason, but he's one Devonta Freeman concussion away from having a sizable role in an offense built around a two-back attack.
Marcus Murphy, Bills - Murphy had a solid Week 17 last year in place of LeSean McCoy, and even if Buffalo's starter avoids any missed time due to the off-field cloud hanging over his head, Shady breaks down every third year like clockwork -- and his last one came in 2015. Chris Ivory isn't exactly an iron man, either.
Trenton Cannon, Jets - He's got the speed to match his awesome name, and Isaiah Crowell is banged up to begin the year. Bilal Powell is perfectly adequate as a fill-in starter of course, but Sam Darnold needs playmakers, and Cannon could make an impact in limited touches if he gets the ball in space.
Wide Receivers
Kevin White, Bears - The forgotten first-rounder looked good, and most importantly healthy, this preseason. Taylor Gabriel and rookie Anthony Miller aren't big hurdles to clear, and White could quickly win a starting role in an offense with some potential if Mitchell Trubisky makes a Year Two leap.
Tavon Austin, Cowboys - The Rams never figured out how to use him, and it's possible he's just nothing more than a gadget player in the NFL. There are an awful lot of targets up for grabs in Dallas, though, and the depth chart above him is awfully sketchy. It's not out of the question he becomes a poor man's Tyreek Hill in 2018.
Laquon Treadwell, Vikings - Tough to say how many targets could be available for the Vikings' No. 3 receiver behind Adam Thielen, Stefon Diggs and Kyle Rudolph, but Treadwell's size gives him red-zone potential.
Cordarrelle Patterson, Patriots - Tom Brady's turned castoffs into fantasy stars before, and no one's ever doubted Patterson's physical gifts. The fact that he's lasted this long already under Belichick is at least a sign he's matured as a player, too.
Tight Ends
Nick Vannett, Seahawks - Russell Wilson's receiving group is thin, and the QB got used to looking his tight end's way during the Jimmy Graham years. Vannett could be this year's Third-Year TE Breakout poster boy.
Vernon Davis, Washington - Speaking of QBs who like to throw to tight ends, Alex Smith loved hitting Travis Kelce on those seam routes, and while neither Jordan Reed nor Davis have Kelce's size, they can both work the middle of the field very effectively. Only one of them is a walking Questionable tag, though, and it's not Davis.