2015 NFL draft Big Boards: Leonard Williams leads our dueling top 40s

The NFL draft combine signals the real start of draft season, as teams use workouts and interviews to finalize their draft boards. Here at SI.com, we're doing the same.

Below, Chris Burke and Doug Farrar give their top 40 prospects coming out of Indianapolis (you can scroll down to the top 40 or jump straight to the rankings). The below is not a mock draft; the order is based on talent, not where you can expect a player to be drafted come April 30.

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Before getting to the rankings, Chris and Doug break down the toughest player to leave out of their top 10, the hardest prospect to rank and more.

Toughest prospect to leave out of top 10

Chris Burke: Kevin White, WR, West Virginia.

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Finalizing spots 38-40 actually proved more difficult for me than 8-10. That said, White was a case study in how much emphasis we should place on combine results. Headed into Indianapolis, I had Amari Cooper, DeVante Parker and White bunched closely together (in that order) atop the WR rankings. White's 4.35-second 40 time was extremely impressive, but neither Cooper nor Parker did anything to hurt their respective stocks. In fact, Cooper's short-shuttle time (3.98) was a standout mark on its own.

Doug Farrar: Dante Fowler, OLB/DE, Florida.

I ranked Fowler 11th, and I have three pass-rushers—Nebraska's Randy Gregory, Clemson's Vic Beasley and Missouri's Shane Ray—listed above him. Fowler is probably the most gap-versatile of those players, and while I really value players who can make an impact in multiple gaps at any level, I do wonder about Fowler's ability to get off blocks in every area at the NFL level. At 6'3'' and 261 pounds he has the size and speed to be a stand-up linebacker and a hand-on-the-ground defensive end, but I don't always see the ability to penetrate protections that he'll need to be a multi-sack guy in the pros. Fowler is a pursuit player with incredible range for his size and impressive recognition skills, but he tends to over-run on rushing plays. I'd like to see Fowler get a bit more directionally aware, and when he does, he'll be an amazing player. He already is in a lot of ways

Player you think you're higher on than most

Burke: Kevin Johnson, CB, Wake Forest.

Shaq Thompson is probably higher on my list than most, but let's go with the Demon Deacon here. At 6’0’’ and 188 pounds, Johnson does not necessarily fit the current prototype of long and lean cornerbacks. He does, however, check off just about every other box. The 6.79-second three-cone and 3.89-second short shuttle times Johnson posted at the combine highlighted his quick feet, which are evident in how he moves on the football.

Put him in either man or zone and he'll be competitive. Once Trae Waynes and Marcus Peters are off the board, Johnson should be among the next in line.

Farrar: Danny Shelton, DT, Washington.

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I know defensive tackle isn't generally a No. 1 overall position—heck, Ndamukong Suh had to wait until the second pick in 2010 when he was the most dominant college player I'd ever seen. Three defensive tackles (Buck Buchanan, 1963; Russell Maryland, 1991; Dan Wilkinson, 1994) have been selected first overall in the history of professional football, and Shelton won't be the fourth—at 6'2'' and 340 pounds, he doesn't check all the athletic boxes. But I haven't seen better overall tape from any player in this draft class. Shelton had nine sacks and 16.5 tackles for loss in 2014, despite the fact that he was double-teamed on nearly every one of the snaps he took. And he took over 80 percent of Washington's defensive snaps in 2014—that's a rare number for a big man. Shelton can destroy pockets, he'll use his surprisingly quick feet to get past blockers and he works very well from multiple gaps. I don't think there's an NFL team that wouldn't benefit tremendously from Shelton's addition, and in my opinion, there isn't a player in this draft with more overall value ... once you take the quarterback value equation off the board. And once his NFL team teaches him a wider array of hand moves, Shelton will be absolutely lethal.

Hardest prospect to rank

Burke: Bud Dupree, DE/OLB, Kentucky.

Another combine star (4.56 40, 42-inch vertical, 11-feet-6 on the broad jump). He is well-built at 6’4’’, 269 pounds and finished his Kentucky career with 37.5 tackles for loss and 23 sacks. It's easy to see why so many people are high on him entering the draft. But from my vantage point, the hype currently exceeds the performances he had in college, so the projection becomes a little tricky. Oregon's Arik Armstead falls under the same umbrella -- the potential is tantalizing but how long before it's tapped?

Farrar: Andrus Peat, OT, Stanford.

There are times when Peat absolutely kills it on his tape—at 6'7'' and 313 pounds, he has the range and athleticism to dominate enemy defenders at the highest level. He's also a true technician, reminding me at times of D'Brickashaw Ferguson and Joe Thomas. Once he gets his feet set and his arms up in pass protection, it's all over. But I do question Peat's ability to run-block consistently, and while I would never question his "finisher's mentality" as some have done, there are times when I would like to see a little more nastiness from him. And it may be easier to get better and more technique than it is to develop that hard-ass edge. I could be wrong about Peat, and I do love his tape overall, but I'd hesitate on picking him unless I was sure that he was going to bring that attitude to my team.

Prospect who left biggest impression at combine

Burke: Vic Beasley, OLB, Clemson.

From the weigh-in on through his workout, Beasley did everything he needed to do. He's a tremendous athlete off the edge, a statement that does not need to be changed at all, apparently, now that Beasley is up to 246 pounds. The sky's the limit.

Farrar: Kevin White, WR, West Virginia.

Kevin White impresses, separates himself from the rest at combine

I loved White's college tape -- he showed over and over that while he doesn't yet run a full route tree, he's got the speed to beat defenders downfield, the vertical ability to make contested catches and should be a real threat in the NFL. Still, some questioned White's separation ability, and whether he was a true No. 1 receiver ... or simply a guy who benefited from West Virginia's wide-open offense. One 4.35 40-yard dash later, and after he looked spectacular in the receiver drills, White showed me that he's more route-savvy and quicker in short spaces than I imagined. In my opinion, White was tied with Alabama's Amari Cooper at the top of the receiver class. But after going back to the tape, I found it hard to stack Cooper on the same pedestal. White reminds me of Randy Moss and Larry Fitzgerald, and it wouldn't surprise me at all if he was selected with one of the top-five picks.

Rankings	Burke's top 40	Farrar's top 40
1	Leonard Williams, DT, USC	Leonard Williams, DT, USC
2	Marcus Mariota, QB, Oregon	Jameis Winston, QB, Florida State
3	Amari Cooper, WR, Alabama	Danny Shelton, DT, Washington
4	Randy Gregory, DE/OLB, Nebraska	Marcus Mariota, QB, Oregon
5	Dante Fowler Jr., DE/OLB, Florida	Kevin White, WR, West Virginia
6	Jameis Winston, QB, Florida State	Randy Gregory, DE/OLB, Nebraska
7	Brandon Scherff, OT, Iowa	Shane Ray, DE, Missouri
8	DeVante Parker, WR, Louisville	Vic Beasley, OLB, Clemson
9	Danny Shelton, DT, Washington	Amari Cooper, WR, Alabama
10	La'el Collins, OT, LSU	Malcom Brown, DT, Texas
11	Trae Waynes, CB, Michigan State	Dante Fowler Jr., DE/OLB, Florida
12	Kevin White, WR, West Virginia	Andrus Peat, OT, Stanford
13	Landon Collins, S, Alabama	Trae Waynes, CB, Michigan State
14	Shaq Thompson, LB, Washington	Landon Collins, S, Alabama
15	Vic Beasley, OLB, Clemson	Brandon Scherff, OT, Iowa
16	Shane Ray, DE, Missouri	DeVante Parker, WR, Louisville
17	Marcus Peters, CB, Washington	Marcus Peters, CB, Washington
18	Todd Gurley, RB, Georgia	La'el Collins, OT, LSU
19	Andrus Peat, OT, Stanford	Todd Gurley, RB, Georgia
20	P.J. Williams, CB, Florida State	Bud Dupree, DE/OLB, Kentucky
21	Ereck Flowers, OT, Miami (Fla.)	P.J. Williams, CB, Florida State
22	Melvin Gordon, RB, Wisconsin	Shaq Thompson, LB, Washington
23	Dorial Green-Beckham, WR, Missouri	Jordan Phillips, DT, Oklahoma
24	Benardrick McKinney, LB, Mississippi State	Sammie Coates, WR, Auburn
25	Malcom Brown, DT, Texas	Melvin Gordon, RB, Wisconsin
26	T.J. Clemmings, OT, Pittsburgh	T.J. Clemmings, OT, Pittsburgh
27	Maxx Williams, TE, Minnesota	Devin Funchess, WR, Michigan
28	Kevin Johnson, CB, Wake Forest	Maxx Williams, TE, Minnesota
29	Eric Kendricks, LB, UCLA	Benardrick McKinney, LB, Mississippi State
30	Cameron Erving, G/C, Florida State	Michael Bennett, DT, Ohio State
31	Devin Funchess, WR, Michigan	Jalen Collins, CB, LSU
32	Arik Armstead, DT, Oregon	Nate Orchard, DE, Utah
33	Michael Bennett, DT, Ohio State	Eddie Goldman, DT, Florida State
34	Denzel Perryman, LB, Miami (Fla.)	Dorial Green-Beckham, WR, Missouri
35	Eddie Goldman, DT, Florida State	Owamagbe Odighizuwa, DE, UCLA
36	Bud Dupree, DE/OLB, Kentucky	Arik Armstead, DT, Oregon
37	Paul Dawson, LB, TCU	Eli Harold, OLB, Virginia
38	Rashad Greene, WR, Florida State	Jaelen Strong, WR, Arizona State
39	Jake Fisher, OT, Oregon	Nelson Agholor, WR, USC
40	Devin Smith, WR, Ohio State	Cedric Ogbuehi, OT, Texas A&M