In most cases, they will be rookies or younger players that have potential to make impacts either this year or within the next couple of seasons. Some may be already on rosters, but could potentially be had on the cheap.
Duke Riley (ATL): I would assume he's rostered in every dynasty format, but if you're able to pry him from his current owner, now's the time. Call me crazy but this could potentially be a Lavonte David / Kwon Alexander type of situation. Remember when David was a perennial top-3 fantasy linebacker? Then Alexander stepped in and started racking up all sorts of stats. Look, Deion Jones is a beast but Riley has already been plugged in as the WLB starter on Rotoworld. That may have been jumping the gun a bit, as the Falcons released their "official" starter package, and, for now Riley is backing up DeVondre Campbell. With Vic Beasley also manning a linebacker spot, Riley could easily see plenty of playing time from the outset, with Beasley better suited for an end/pass rush role. We've seen this defense plenty with what Seattle has done in the past, and Riley fits what they're looking for in this scheme. I've drafted or made attempts at rostering Riley in all my dynasty leagues. Could be a big mistake if he doesn't perform, but there's a good chance he is at least the 1b to Jones' 1a in the next year or two once they figure out how Campbell/Beasley are best used in this scheme.