Top 25 NFL breakout prospects

Adept at rushing and receiving, Andre Ellington is ready to take over the Cardinals' backfield. Jeff Gross/Getty Images

The best NFL organizations don't just find talent in the first and second rounds of the draft. They find talent with their later picks and with their unsigned free agents. For the best example, look no further than the reigning Super Bowl champions. Quarterback Russell Wilson, of course, was a third-round selection. So was defensive tackle Brandon Mebane. The Seahawks got half of the Legion of Boom in the fifth round: Kam Chancellor in 2010, and then Richard Sherman in 2011. Malcolm Smith, the Super Bowl MVP, was added in the seventh round. And receivers Doug Baldwin and Jermaine Kearse were both undrafted free agents.

Every year since 2007, Football Outsiders has put together a preseason prospect list to highlight the lower-drafted players who are set to make a much larger impact in the seasons ahead. For the uninitiated, our "top prospects" list is not like the prospect lists you read about in the world of baseball. Since the top prospects in college football are stars on national television before they get taken in the first round of the NFL draft, there's not much utility in listing them here. Everyone knows who Sammy Watkins and Johnny Manziel are by this point. Instead, we use a combination of statistics, scouting, measurables, context, and expected role to compile a list of under-the-radar players we expect to make an impact in the NFL, both in 2014 and beyond.

We limit the pool to players who fit the following criteria:

• Drafted in the third round or later, or signed as an undrafted free agent
• Entered the NFL between 2011 and 2013
• Started fewer than five career games
• Still on their initial contract with their current team (players who were cut and picked up elsewhere still qualify)
• Age 26 or younger in 2014

Our No. 1 prospects have included Miles Austin (2009) and Mike Wallace (2010). Last summer's edition included T.Y. Hilton at No. 3. However, this isn't strictly a fantasy football list; defensive players who have been featured on our list before they became regular starters include Geno Atkins, Morgan Burnett, Elvis Dumervil and Cortland Finnegan.

You'll see a number of references to Football Outsiders stats on our list, in particular DVOA (defense-adjusted value over average), which takes every play and compares its success to the NFL average based on situation and opponent. You can read more about that and other FO stats on this page. You'll also see a few references to Football Outsiders' systems for projecting college talent to the pros. To learn about those systems, click these links for playmaker score, SackSEER and speed score.

1. Andre Ellington, RB, Arizona Cardinals

The Cardinals primarily used two running backs last season. One of them, veteran Rashard Mendenhall, averaged a dismal 3.2 yards per carry with a minus-10.2 percent DVOA. But running behind the same line, sixth-round rookie Ellington averaged 5.5 yards per carry with 17.5 percent DVOA. Now Mendenhall is gone, and Ellington is the starter and a clear workhorse for the Cardinals. We were worried about Ellington coming into the NFL, since he ran the 40-yard dash in 4.61 seconds at 199 pounds, leading to a speed score of just 88.1. However, he may have just been having a bad day; that time improved to 4.51 at his pro day, for a better speed score of 96.1. And he's certainly shown great speed getting to the edge so far in his NFL career; perhaps his speed just shows better running laterally instead of running straight ahead on a track with no blockers or defenders. Much like the similarly sized Jamaal Charles, Ellington is a great receiver as well as runner. He can catch passes out of the backfield, but can also be split out wide or used on bubble screens. Last season, he caught 39 passes for 371 yards, nearly 10 yards per catch with 22.3 percent DVOA. Ellington's not going to average 5.5 yards per carry every season, but he's definitely a potential star in the making.