Former Blue Devil wide receiver Eron Riley proved through his four years at Duke that he had size, excellent hands and big play ability, but most draft evaluations of the 6-foot-3, 185-lb. wideout raised doubt as to whether he had the top-end speed necessary to succeed at the next level.

Riley may have put some of those doubts to rest at Duke's Pro Day on Monday.

In front of NFL scouts and player personnel officials, Riley apparently ran a 4.36 40-yard dash, head coach David Cutcliffe said Tuesday. The tryout was closed to the media so we at the Sports Blog didn't see the drill firsthand, but a legitimate sub-4.4 40 time is likely to provide a crucial boost to Riley's stock a little more than a month away from the NFL Draft on April 25-26.

More than perhaps any other metric in football talent evaluation, the 40-yard dash can either make or break a player's draft hopes. A quick 40 time could lead a player to jump all the way to the first round, while a misstep or poor time can mean that a marginal draft prospect won't even have a shot at being selected in the late rounds.

That said, there is plenty of debate about how legitimate 40-times are and what role they should play in the evaluation process of pro prospects. Legend has it that Deion Sanders once ran a 4.17 40-yard dash while wearing high tops during his Florida State pro day in 1989. 40 times as fast as that these are almost always recorded on hand-held stopwatches, which can bring into question the legitimacy of such measurements. According to an excellent April 2005 piece on the 40-yard dash by Mark Zeigler of the San Diego Union-Tribune, the margin of error that must be taken into account with hand-timed 40 times is surprisingly wide:

Say someone clocks a hand-timed 4.35 in an NFL workout.

The accepted standard to convert a hand-timed event to its automatically timed equivalent is to round up to the nearest tenth of a second – in this case 4.4 – and add .24 seconds. Now you're at 4.64.

Most football 40s don't go on a starter's pistol but on an athlete's motion. The average reaction time among elite sprinters (from the gun to the moment they exert pressure on the starting block's electronic pads) is about .15 seconds; for a football player with little track experience it probably would be closer to .2. Add that in, and you have 4.84.

Now say it's a breezy day and you're running with a tailwind. Say it's 10 mph. Accepted track tables say that would provide a .07-second advantage over 40 yards. Add it in, and your 4.35 is suddenly a 4.91.

Electronic timing systems can overcome some of these obstacles, and such a system has been in place at the NFL Combine since 1990. But with an increasing number of players eschewing a run in Indianapolis for the friendly confines of their respective Pro Days, the 40-time numbers coming off the scout's stopwatch might be the only information available for talent evaluators.

So with these factors in mind, the absolute time value of a player's 40 time may be less important than how he comparatively stacks up to others at his position. It's hard to find a database of other prospects' hand-timed Pro Day 40 times, but just for discussion's sake, let's go ahead and consider Riley's 4.36 as legitimate as an electronically timed 40-yard dashes from Indianapolis . Stacking it up against the times from other wideouts at February's NFL Combine, Riley would boast the 4th fastest time at his position—even ahead of Florida speedster Percy Harvin, who ran a 4.41.

We won't know for sure until late April, but Riley's run Monday may have eliminated the main red flag that draft analysts have raised against the former All-ACC wideout. What do you think about Riley's pro prospects? Do you think he has what it takes to stick on with an NFL team?