Sleeper is going to mean different things to different leagues. I'm in 12, 14, and 16 team leagues so players that don't get drafted in the 12-teamer are still valuable picks in the 16-team league. I think what we're looking for here is players that will out perform their ADP.
I've mentioned Joe Mixon in another thread. There are several reasons why he should have a better year than the RB16 he's being drafted at. The Bengals OL has been improved. They get an offseason with their offensive coordinator, and the Bengals showed they are willing to use him as an every down back as he received over 70% of the RB touches when he was healthy and in the starting role.
Alex Collins is another who put up really good YPC numbers and when he was given enough carries he did good things with them. This was all while running behind an OL missing it's best player. I would expect the Ravens offense to be better this year as well with the signing of Crabtree and their new 1st round TE opening up the field some more. Hes currently going at RB19.
I think Dion Lewis is a steal at RB26 in PPR. I don't think Henry is anything special and I've heard the statement that people expect Lewis to get fewer touches but compile more yards. He's 8 RB spots below Henry in RB ADP and I think at the end of the year he'll have more fantasy points.
Mark Ingram at RB 23 - when you consider that you're getting a discount for the games he'll be suspended and you know that you have to draft to deal with that, his ADP for his projected points per game is a bargain.
If you're drafting now, Royce Freeman at RB 27 is a steal as the tea leaves seem to indicate he'll have most of that RB workload. However I suspect his ADP will be closer to RB 15 by the time most of us draft
Aaron Jones at RB 40. Yes you have the 2 game suspension and that could delay his productivity, but it's obvious Montgomery can only sustain so many touches per game. I may be getting this stat wrong, because I heard in on the radio, but Jones had around 15 carries of 15+ yards (he definitely had 8 of 20+) Williams had.... One. Jones is the best runner of the green bay running backs. if logical coaching prevails, he's the RB to own in GB.
Also Nick Chubb at RB 42 could be a huge steal. I think Cleveland will improve to some degree, even substantially if Mayfield can play early and be effective. Chubb, by most reports I've read was the 2nd most NFL ready back in the draft. Cleveland O-line wont be bad even with the loss of Joe Thomas.
Chris Carson at RB 51. For the last couple of years Seattle has had no real effective ground game. Carson was very good when given the opportunity before his injury. It should be noted that Penny's lack of blocking ability has been noted in multiple reports. I know Wilson is elusive but in order to be on the field Penny will have to block some. The early reports were that Carson still looked to be the better back. Teams don't spend 1st round pick on bench players though, so this could be a reach.
Nyhiem Hines was mentioned above but I really liked him at NC State and in a PPR league I think he could be an RB3.
For deep leagues I think Justin Jackson is a good late flyer as there are some who feel Melvin Gordon doesn't do enough with the volume of work he's given. Jalen Samuels was mentioned for his potential role in the event Bell has an extended holdout or is re-injured.