The NFL combine begins tomorrow. NFL personnel folks will be riveted to see just how fast, explosive and strong the top draft prospects truly are; millions of dollars potentially hang in the balance. With so much money on the line, many of the prospects have spent weeks training at specialized combine prep facilities to get ready for this week. I spoke to Tony Villani, a trainer who is the founder of XPE Sports (Explosive Performance Enhancement) in Boca Raton, Fla., about this kind of training. Villani has generated quite a buzz in recent years for his work with some of the fastest-rising talent at the combine. This year he has (among others): a possible top-five pick (Eric Berry from the Tennessee Volunteers, whom I profiled for ESPN The Magazine this year) and two candidates with a good shot at being the fastest man in Indy this week (Jacoby Ford from the Clemson Tigers and Jahvid Best from the California Golden Bears). Villani also spoke about the challenges of training a track guy for the 40-yard dash, what separates Berry from other super-athletic safeties, and the viability of someone actually running a 40-yard dash in 4.1 (the fastest at the combine in recent memory is Chris Johnson of the Tennessee Titans, who ran a 4.24, video of which is here). In addition to Eric Berry, Jahvid Best, Eric Norwood and Dan Williams, how many players will you have working out at the combine this year?We have 16 guys invited to the combine this year, which is more than I've ever had. I was hoping to have about 12 this year, but I wasn't expecting this many because I just moved to Florida. And because of the move, I couldn't really market what our facility was. Why do you think there has been such an increase in the number of top prospects coming to you this winter?Normally what I would do is talk to a handful of guys myself. This year I talked to about a dozen. I'd go through the pitch as most companies do: "This is our facility. You'll eat this. You'll do that." Out of those 12, I figured about six would come and then agents would fill in another six spots. Well, this year I really couldn't talk about the facilities, so all I talked about was the published results from the combine in 2008 and 2009 and how my guys did. Every guy I spoke to, I said, "These are the exact results from Indianapolis. Look into them." And all 12 guys I talked to ended up coming. And then some agents filled in another six to eight spots. I have 12 combine guys and about 20 total. The results really helped sell some of the big-name guys, which was good.Last year, we had a safety that the Miami Dolphins drafted in the fifth round named Chris Clemons. From the safety position, he ran faster than any of the 60 or so DBs in attendance there. Sherrod Martin was a safety who was supposed to go in the fourth or fifth round, and he worked out so well in that he had the second-fastest shuttle and 3-cone time that they looked at him at DB and he went second round. The year before that we had three guys go in the top 15 that were all projected to go second or third round before they came to Indy.