Pro days will be in full swing this week, and as several players go through their workouts and have their results posted, you might notice something a little strange in the numbers.
Many of the 40 times posted at pro days might be slower or faster than the times you saw at Indianapolis for the NFL Scouting Combine. It's important to understand why.
In 1970, the Dallas Cowboys gave a $25,000 grant to Penn State Unviersity to do a comprehensive study on 40-yard dash times related to surface as well as the shoes used for running these sprints. The results were interesting and showed that, sure enough, running on grass resulted in slower times than running on turf, like the kind they had at Lucas Oil Stadium, the site of the combine -- on average, the times on grass were about .12 seconds slower than on turf.
So for example, if a player runs on grass and posts a 40 time of 4.65, he's going to run about a 4.53 on turf. Teams take this into account when they track 40 times that are run on different surfaces, and like to convert the times to a uniform surface when they sort the numbers.
The Penn State study also found that there is a slight difference in times when players run in cleated football shoes, which are traditionally used on grass, and spiked shoes. Runners who used spiked shoes ran about .03 seconds faster. That means that a guy who runs a 4.65 40 on grass and in football shoes would have a time of about 4.50 on turf and in spikes.
Keep this in mind as you're looking through the 40 times from pro day, and don't be surprised if there's a difference in the numbers from Indianapolis.
Here's a quick rundown of this week's pro-day workouts, and the one or two things I'll be most interested in for each one:
» Auburn (Tuesday): Steven Clark was a semifinalist for the Ray Guy Award the last two seasons and is one of the top punters in the draft. He performed at the combine, but I'm interested to watch him punt outdoors on his pro day.
» Buffalo (Tuesday): Khalil Mack was one of my nine standouts at the combine and has been one of the draft's biggest risers. I want to see how many people are there on his pro day to watch him do pass-rushing drills.
» Arkansas (Wednesday): Chris Smith played defensive end at Arkansas but was tried as a linebacker at the combine. He's short but has good quickness, and I'll be interested to see him do more linebacker drills here.
» Texas A&M (Wednesday): Mike Evans posted a strong time in the 40 at the combine (4.53 seconds) and impressed some with his route running. I want to get a better look at both, especially his route running, which I've had issues with in the past.
» Wisconsin (Wednesday): Dezmen Southward, who played free safety for the Badgers, didn't participate in drills at the combine, so I'll be looking to see how he runs and jumps and performs in all of his field drills on his pro day.
» Clemson (Thursday): Martavis Bryant was known as the "other" receiver at Clemson because of star Sammy Watkins, but I was impressed with his performance at the combine, especially in the 40-yard dash, where he ran faster than I expected (4.42 seconds). I want to learn more about him, as well as defensive back Bashaud Breeland.
» Wyoming (Thursday): Marqueston Huff played both free safety and cornerback at Wyoming, and I've liked him for some time. On his pro day, I want to see if he can be a slot cornerback.
» Northern Illinois (Friday): Jimmie Ward didn't participate in drills at the combine. I want to get a better look at him here in several drills to see if he can be a top safety.
» Ohio State (Friday): Ryan Shazier was expected to post a strong time in the 40 at the combine, but he didn't run in Indianapolis. I'm really interested to see how fast he runs on his pro day. I also want to work out backup quarterback Kenny Guiton, who was not at the combine.
» Louisiana Tech (March 10): IK Enemkpali is 6-foot-1, 261 pounds. He played defensive end in college, but I want to see if he can be a 3-4 linebacker.
» Kansas State (March 11): Luke Lucas is an offensive tackle with great size at 6-foot-8 and very long, 36 3/4-inch arms. I really want to study the tape on him, and I also want to watch Ty Zimmerman, who was a defensive back in college, work out as a wide receiver; he was not at the combine.
» Michigan State (March 11): Darqueze Dennard didn't have a great combine workout, so my main interest on this pro day will be to get a good, close at him in all of the drills. I also want to find out if LB Max Bullough has a position, and learn more about his off-field problems.
» UCLA (March 11): Anthony Barr lacked strength (15 bench reps) and had a good-not-great workout at the combine, so I want to see if he can perform better here. I'll also be watching one of my favorites, Xavier Su'a-Filo, who I expect to be a top starting guard in the NFL.
Follow Gil Brandt on Twitter @Gil_Brandt.