Arm strength, speed, jumping ability, and yes, hand size. All of these attributes -- and many more -- are on display for scouts and coaches at the 2014 NFL combine. But can a football player really hurt his draft stock with a poor performance? And does a bad combine affect a rookie's paycheck?

Yes, though there's a caveat. 

An expert's opinion
Steven Burkett, the CEO of Eye-Scout, a software company that specializes in pro athlete evaluation, talked to me about the combine in greater detail. 

According to Burkett, it's really the culmination of an annual process. Organized by National Football Scouting (NFS), Burkett compares the combine to an end-of-year dance recital. "NFS works year round at scouting the college athletes and establishing the player pool," he explains, "and the combine is the big showcase ... where the athletes get to show off."
Burkett says each NFL team should go into the combine without any biases or favorites, which, it appears, indicates two possibilities: If a player has a good combine, his draft stock can rise, and if it's shockingly bad, he can be left waiting when the clock starts ticking.

Image via Marianne O'Leary, Flickr.

Looking back
NFL drafts of years past are chock-full of examples where combine performances differed from the media's expectations -- for better or worse -- and rookies' contracts were affected.

In 2005, for instance, Matt Jones was a 6'6″ QB many projected as a middle-round pick, but a ridiculous combine -- he ran a sub-4.4 40 -- earned him ESPN's designation as the "best player in the draft." After being picked in the first round by the Jacksonville Jaguars as a wideout, Jones signed a five-year, $8.5 million contract -- a 200% premium to what most mid-round picks got that year, according to Spotrac.

Defensive end Dwight Freeney in 2002, and corner Dominique Rodgers-Cromartie translated combine domination into first-round success as well, signing multi-million rookie contracts much higher than most expected.

On the other side of the coin, it appears the combine can damn draftees as well, such as Vontaze Burfict in 2012. The linebacker was initially projected as a top five pick by some journalists,  but a slew of problems -- an awful 40 time, poor interview skills, and a failed drug test -- preceded him being left him out of the draft entirely. By the time the Cincinnati Bengals signed him to a three-year, $1.4 million contract as an undrafted free agent, he was making about 75% less than the average first-round rookie linebacker.

Delving deeper
Based on a scan of players who had tough combines, it appears these issues aren't limited to certain positions.

 PositionPre-Combine Est. Round DraftedActual Round Drafted
Damontre Moore DE 1st 3rd
Michael Brockers DT 1st 1st
Nick Fairley DT 1st 1st
Manti Te'o LB 1st 2nd
Vontaze Burfict LB 1st Undrafted
Mohamed Sanu WR 1st 3rd
Joe Adams WR 2nd 4th
Mike Adams OT 1st 2nd
Dwayne Allen TE 1st 3rd
Stepfan Taylor RB 3rd 5th
Colin Kaepernick QB 2nd 2nd
Tyrod Taylor QB 6th 6th

Sources: Spotrac, Bleacher Report, and various media sources. Bolded figure represents a perceived loss in draft value post-combine.

The 12 players listed above have been widely cited by the media as combine disappointments in recent years, and they cover nearly every spot on the field. In Colin Kaepernick's case, Bleacher Report called his throwing session in 2011 "erratic," while Stepfan Taylor's 40-yard dash was reported "slow." Manti Te'o, meanwhile, had what ESPN called a "disappointing" sprint time last year.
In some cases, one bad day can be very expensive. The largest difference in draft position, by far, is between a first and second round pick.
RoundAnnual Average*
1st $4.4 million
2nd $1.4 million
3rd $857,000
4th $753,000
5th $632,000
6th $591,000
7th $566,000

Source: Spotrac. *Annual average from 2013 draft, includes signing bonus.

The caveat
Of course, this analysis is under the assumption pre-combine mock drafts and media reports are always accurate. What if they weren't?
I spoke with Mike Hagen, a veteran NFL scout who works with Competitive Sports Analysis, about this possibility. "The main focus of the evaluator at the combine is to verify what he's seen before," Hagen told me. He says many scouts "already know" if a player is training poorly, or is coming off a subpar college season. Burfict, for example, already had some warning signs, according to Hagen. 
There's no denying athletes who experience a poor NFL combine sometimes are drafted lower, and paid less than the media expects. But remember, the combine is really the culmination of a year's worth of work. It isn't crazy to think some scouts are ahead of journalists when it comes to player analysis.

Looking ahead
Going forward, the combine could be affected by one game-changer: big data. Brian Kopp, a senior VP at STATS, told me that the company's X-Info analysis system is already being used by 12 NFL teams and a handful of college football programs. 

Much as it's doing with player tracking in the NBA, STATS offers NFL decision makers more analytical ability, and with a client list that Kopp says is "growing by the week," it may not be long before the majority of league is involved.

More data likely means more transparency, something that could make the media's mock drafts more accurate. If the average blogger is able to better understand the rationale a scout uses, projections could be improved. That's something everyone can get on board with.