A sleeper can take a good season and make it unforgettable. Each year we're looking for the next Devonta Freeman, David Johnson, and Arian Foster. Before these guys became fantasy MVPs, they were drafted in Round 10 or later in many fantasy drafts. Here are some of the guys that have the potential to finish significantly ahead of where you'll likely to draft them.
Martellus Bennett, TE - New England
The Patriots are very dangerous in 2-TE sets, and ESPN's Mike Reiss thinks the Pats could use that setup on up to 80% of their snaps. The combo of Gronk and Bennett is going to be very difficult for defensive coordinators to plan for. Rob Gronkowski is going to cost you a first or second round pick. Bennett is going in the 11th round. Gronk will get you ~4 std fantasy points for every auction dollar versus Bennett's ~58 points for every auction dollar. Gronk is projected for 174 points (STD scoring) and Bennett is projected for 116 points. Is there any better value at TE? He'll be drafted as a backup fantasy TE, but don't be surprised to see him end the season as a TE1.
Jared Cook, TE - Green Bay
I've seen Cook on the field, and he reminds me a lot of Jermichael Finley...only better. Cook may be one of the most underrated players on fantasy draft boards this year. His preseason action has been great and he has seen most of the first team work ahead of Richard Rogers. After spending the last seven years catching passes as a Titan and Ram from a multitude of average throwers, he's finally going to get an elite QB under center. After Nelson and Cobb, it's not unrealistic to think that Cook becomes the 3rd-most targeted guy in Green Bay. Look for Cook to go in Round 13 or 14 as your backup TE with TE1 upside.
Michael Thomas, WR - New Orleans
HC Sean Payton said he would draft Michael Thomas if he played fantasy football. In one of the NFL's most pass-happy offenses, Michael Thomas has an opportunity to contribute mightily in his rookie year, particularly in the red-zone. He has to compete with Cooks, Snead, Coleman, and Fleener for targets, but the comparisons to Marques Colston continue. With an FFN ranking of 52nd among all WR's, he's likely to be your WR4 or WR5.
Mohamed Sanu, WR - Atlanta
Sanu is the clear #2 receiver in Atlanta opposite Julio Jones. He's filling the role vacated with the departure of Roddy White. Sanu is going around the same spot in drafts as Michael Thomas listed above, but unlike Thomas, his spot on the depth chart is clear. The concern with Sanu is that he'll have the issues with drops like he did in Cincy, but so far this preseason, that hasn't been an issue. The potential for Sanu is great and should be a great WR4/5 flier.
Devin Funchess, WR - Carolina
When Kelvin Benjamin went down before the start of last season with a torn ACL, expectations for Funchess ratched up. He finished the year with 31 receptions for 473 yards and 5 scores - not exactly lighting the world on fire, but it won't take much to improve upon those numbers. Every preseason scouting report has praised Funchess including Panthers' WR coach Ricky Proehl who said that Funchess is definitely pushing Benjamin for a bigger role. Although he's playing behind Benjamin and Ginn right now, he should play that bigger role as the season progresses. He's another WR4/5 that could easily outperform his ADP.
Tyrod Taylor, QB - Buffalo
Taylor is less of a sleeper as the season approaches than he was a few weeks ago. This is because people are starting to realize that he has the potential to be your QB1 and can be picked up at QB2 value. He has a healthier Sammy Watkins back this year and is fresh off a six-year, $92 million deal. He needs this year to be a monster to get the long-term commitment he wants. Taylor can put points up for you with his arm, but just as exciting, with his feet. He was second only to Cam Newton in QB rushing yards last season.
Devontae Booker, RB - Denver
There's a good chance that Booker surpasses Ronnie Hillman on the depth chart this year and serves as the top backup to CJ Anderson. In PPR formats, Booker has the potential to shine as the pass-catching back. His ADP has him going in the 11th round while his FFN ranking has him in the 13th round, so he's being drafted ahead of his ranking.
DeAndre Washington, RB - Oakland Raiders
Washington looks like he may have the #2 spot on the depth chart locked up after rushing 8 times for 55 yards and a 6-yd TD pass in the Raiders' third preseason game. He should prove to be a great compliment and change of pace back to Latavius Murray. You'll be able to find him after Round 11.