For those invited and participating in the 2015 NFL Combine, what matters? What’s the most important thing to watch out for? They’re all talented and they all have elite skills, but there are keys that every scout and GM will be looking at. Here’s what each prospect has to prove … 

1. Todd Gurley, Georgia 6-1, 226 
Can he deal with the physical? He’s still trying to get healthy, and he needs to show that there’s still going to be healthy enough to be worth the investment. Teams are going to have to fly blind when it comes to picking him, so it’s going to be an interesting call – will he be the same back, or better, with a fully-healed knee, and will he be able to stay in one piece? 

2. Melvin Gordon, Wisconsin 6-1, 213 
His hands. Fumbles are a problem at times, and he wasn’t that big a part of the passing game on a regular basis. Strength and blocking ability will be watched out for, too. A big 40 time would be nice to show off some top-end speed. A 4.6+ won’t be disastrous, but it could drop him to the late first round or early second. 

3. Jay Ajayi, Boise State 6-0, 216
Just how much tread is there on the tires? He was used, used, overused, and used some more. There’s a chance he could become the first back taken in the draft with a few great workouts, but the physicals are going to be vital. 

4. Tevin Coleman, Indiana 6-1, 210 
How fast is he? He plays more of a speed game than a power one, and he’s big in open spaces, but he’s not a normal NFL workhorse. If he’s going to be the type of fast runner who busts off the occasional home run, he has to show off the deep wheels. 

5. T.J. Yeldon, Alabama 6-2, 221 
Can he hit? He’s a big back who doesn’t play with enough power or toughness. Is he good enough at any one thing or in any one area to be a special NFL runner? There are just enough question marks – fumbling? – to knock him down a few pegs, so he has to come up with a great weekend. 

6. Duke Johnson, Miami 5-9, 206
Does he have any power or strength? As a speed and quickness back, he has to dominate the speed and quickness drills. The physicals will be a big deal after getting beaten up over his Miami career – there are going to be some big durability red flags. 

7. Ameer Abdullah, Nebraska 5-9, 195 
The 40. Of course, the quickness and short drills are really more important, but considering Abdullah’s lack of bulk – and with no ability whatsoever to get bigger – he had better fly. He’s going to be sold as one of the best all-around backs in the draft, but he has to shine as an exploder. That has to come with a 4.4. 

8. Javorius Allen, USC 6-1, 220 
The second-level burst. He’s fast and quick for his size, and while he doesn’t bring enough power, he’s okay. However, does he need to gear back up after his first cut? Interviews are going to be key – he has to sell the idea that he’s going to be a killer who can handle the NFL workhorse rigors. 

9. Mike Davis, South Carolina 5-9, 223 
Interviews. There was something that just didn’t quite mesh with Steve Spurrier at times, and he’s going to have to prove that he’s ready to sell out to become special. He has the compact frame, and he could be someone’s favorite running back sleeper, but his draft stock depends on how he comes across. 

10. Cameron Artis-Payne, Auburn 5-11, 210 
Does he have the lateral quickness to bounce to the outside? He’s a tough, between-the-tackles runner who can crank out yards and chunks, but he needs to show hands, route running ability, and the fluidity to do a little of everything right. 

11. Karlos Williams, Florida State 6-1, 225 
Is he a running back? Is he going to rock the interviews? There was an off-the-field incident that GMs will have to dive into and have to ask about, even if he wasn’t charged with anything. On the field, the former defensive back has to show off the finer points of being a running back after showing flashes of greatness on offense. 

12. David Cobb, Minnesota 5-11, 220
Is he a one-note back? He’s tough, powerful, and grinding, but that also screams Short Shelf Life at the next level. If he comes off as an athlete and isn’t plodding, he’ll up his stock in a big way. He also needs to look the part as a receiver. 

13. David Johnson, Northern Iowa 6-1, 229
With his size and his bulk, he needs to be fast. He might not be as powerful as he should be for back of his size, and he could stand to look the part of a power back, but the scouts are going to want to see the raw athleticism to go along with the great tape and a strong Senior Bowl week. 

14. Jeremy Langford, Michigan State 6-1, 208 
If there’s a way to show more pop and power, he’ll have to. He’s fast, athletic, and productive for his size, and he can catch, but for his style he needs to be laterally quick and it wouldn’t be a bad thing if he hits the bench hard. 

15. Matt Jones, Florida 6-2, 235
Does he have any hope of lasting in the league? A pure power back, no one will question his strength, toughness or pop, but he’s not quick enough and he’s not all that fast. If he can come up with good times and look fluid, he’ll up his stock. 

16. Malcolm Brown, Texas 5-11, 222
Does he have any pop or anything special? He’s going to be seen as a serviceable back, but nothing necessary unless he blows up the stats and the drills – he needs a great workout to make the scouts want to do a deeper look. 

17. Dee Hart, Colorado State 5-8, 189
The physical will mean everything. There’s lots to like, and he has sleeper potential in the mid-rounds, but his knee has to check out. The workout has to be great, and he has to be ultra-quick, but his knee injuries are going to be the issue. 

18. Zach Zenner, South Dakota State 6-0, 220
The numbers have to be great. He has looked the part of a big-time school runner despite the small-school tape, but there’s nothing really slick about his game. If he can look fluid and quick in any way, his stock will quickly shoot up. 

19. Josh Robinson, Mississippi State 5-9, 215
He has to look athletic. A bowling ball of a runner, he can run well and has power, but there isn’t anything too creative about his style. He needs to surprise and show some potential with some great 40 and quickness drill times. 

20. Kenny Hilliard, LSU 6-0, 232 
Does he have the lateral movement and quickness? He’ll blast away, but he might never be seen as anything more than just a power back if he can’t come up with some excellent numbers in the speed and agility drills. 

21. Dominique Brown, Louisville 6-2, 241 
Does he have the speed to go along with the power, and does he have the strength to go along with his size? More than that, he has to show the GMs that he’s worthy of being a mid-range pick after falling off the map over the second half of last year. 

22. Michael Dyer, Louisville 5-9, 215
The interview process means everything. There’s the potential to be a great part of a rotation – he could be a far better pro than a college player – but the character issues are going to be more than just a red flag for some teams. 

23. B.J. Catalon, TCU 5-9, 190
The pass catching skills have to come out. He’s going to be pigeon-holed as a third-down back so the more he can look the part as a receiver and the quicker he looks, the more creative the scouts are going to get with him. 

24. John Crockett, North Dakota State 6-0, 202
If there’s a way to show strength, he needs to do it. The bench doesn’t really matter, but the explosion in the jumps and power in his legs have to come through. He has to look like a receiver, too. 

25. Thomas Rawls, Central Michigan 5-10, 217
The workout has to be great, but the interviews will be more important. He has the tape, and he has the skill, but off-the-field issues this season will be what everyone wants to look into. Injury concerns and health will make the physical a big deal, too. 

26. Trey Williams, Texas A&M 5-8, 195
He’s better bring it in the 40 and the quickness drills. With no size and a questionable move to come out early, he needs to wake up the scouts by looking like a flash of lightning. 

27. Jahwan Edwards, Ball State 5-9, 215
Already a shifty back, he needs to stand out in some way with his quickness and speed. He can do a little bit of everything well, but can he be special? Something has to excite the scouts. 

28. Braylon Heard, Kentucky 5-11, 189
Can he look like an NFL running back? He’s built like a slot receiver – which he might turn into – and he’s going to time well, but the stronger he can appear, the better. 

29. Marcus Murphy, Missouri 5-8, 188
The hands have to be there to look like a possible third-down back, and the more he can appear to be a kick and punt returner, the better. He’s quick – he has to time really, really quick. 

30. Joey Iosefa, Hawaii 6-0, 245
There’s one thing he can do well – power the ball – but if he can be quick in the short drills and show good blocking toughness – at least compared to the other backs – he could be seen as a possible option as both a fullback and an H-back.