My personal team is the Vikings. No sleepers jump out for them at the moment but here's my take on some guys:
Dalvin Cook
was never really a sleeper but his value is increasing by the day given his practice performance and Murray's injury. Guy has gone from a top 25 RB to Top 15 imo.
Adam Thielen
Not as under the radar as he used to be but still valued pretty low and going later in drafts. I think I actually prefer him to Diggs. Diggs will catch 10 balls one game and 2 the next. Thielen is going to give you 5 catches per game and is probably more likely to catch a deep one than Diggs. Treadwell doesn't scare me, I've practically already written him off as a bust, especially since he got hurt again. I wouldn't worry too much about Michael Floyd's return from suspension in October either.
Rest of the league:
RB
Packers RB not named Ty Montgomery -
This still isn't sorted out yet but whoever wins that number 2 job in GB between Jamal Williams, Aaron Jones and Devante Mays is someone I would look at.
Marlon Mack
Frank Gore is old and Robert Turbin isn't anything to write home abbout. Nice draft and stash guy.
Kareem Hunt
If he didn't already pass C.West on the depth chart, he will and think he eventually eats into Ware's carries.
Shane Vereen
Like someone said above, I don't think the staff is that high on Paul Perkins, he's someone I'd look at, especially in PPR.
Samaje Perine
Robert Kelley doesn't impress me, Chris Thompson is a 3rd down back and Matt Jones is going to get cut. I think he takes the job by midseason.
WR
Andre Holmes
Going to start on the outside for the Bills. I know they drafted Zay Jones and picked up Boldin and Matthews, but I think they bring Jones along slow, Boldin's role is probably going to be similar to that on Lions last year and Matthews is pretty much only a slot guy.
Robby Anderson
I know the Jets are god awful but someone has to catch the ball for them. He's the defacto #1 for now. ArDarius Stewart has been banged up in camp, but he might also be someone to look at.
Kenny Golladay
Another guy who's been tearing up camp. Tate and Jones are the starters, but he might grab that Anquan Boldin role for them. Might be TD or bust early on though.
Cameron Meredith
He was good last year when they still had Jeffery and is going to start. The rest of their WRs are underachieving/injury prone guys like Markus Wheaton, Kevin White and Kendall Wright.
I really liked Cooper Kupp for the Rams too, but then the Watkins trade happened. Might still keep an eye on him though because Watkins is injury prone, Robert Woods sucks and Austin is a gimmick player.