Talent is the most important quality that scouts look for on draft day. Durability rates a close second.
A poor medical grade can be more disastrous than almost any character flaw or off-field incident. Medical testing -- not the infamous 40-yard dash, vertical jump or bench press -- is the primary reason why more than 300 potential NFL players are annually invited to Indianapolis for the mental and physical inquisition known as the NFL Scouting Combine.
"No question, the most important element of the combine is the medical testing done there," one longtime NFL executive shared with NFLDraftScout.com.
Two years ago, Clemson defensive end Da'Quan Bowers, once considered a potential top-five pick, slipped to No. 51 overall due to medical red flags. Similarly, Washington running back Chris Polk, viewed as a potential second- or third-round value a year ago, fell all the way out of the 2012 draft.
And with the 2013 draft class lacking elite star power, the scrutiny over medical testing is even more intense.
Since the end of the 2012 college season, NFLDraftScout.com has been tracking the progress of three highly regarded defenders whose medical tests could prove to be the final hurdle preventing them from fulfilling the dream of playing in the NFL.
As first-team all-conference selections, Utah defensive tackle Star Lotulelei, Georgia pass rusher Jarvis Jones and Houston cornerback D.J. Hayden possess the size, athleticism and playmaking ability to dominate at the collegiate level.
Other than talent, the three defenders share another connection -- they've all been taken off the draft board of at least one NFL club, NFLDraftScout.com has learned through multiple sources.
The winner of the 2011 Morris Trophy as the Pac-12's most dominant defensive lineman, Lotulelei might be the most aptly-named athlete in the draft. While unable to repeat as the conference's defensive lineman of the year as a senior, the Utah defensive tackle established himself as a bona fide "star" in racking up 42 tackles, 10 tackles for loss and five sacks despite facing constant double- and even triple-team blocks.
Lotulelei steadily held his status as the top-rated senior defender on my Big Board.
But routine medical testing conducted at the combine uncovered that the left ventricle in Lotulelei's heart was only operating at 44 percent efficiency, as opposed to the normal 55-70 percent range. When the NFL learned of the test result, Lotulelei wasn't allowed to work out at the combine.
The "combine re-check" -- a review of medical progress and analysis of flagged conditions such as Lotulelei's -- will be in Indy on April 5-6. Lotulelei is among the players who will be tested there.
NFLDraftScout.com has confirmed through a source close to Lotulelei that he will participate in Utah's Pro Day workout on Wednesday. The fact that he will run drills on campus, however, does not necessarily mean NFL team doctors are willing to sign off on him playing football.
In fact, NFLDraftScout.com has learned that multiple NFL teams view the two-time first-team All-Pac-12 defensive tackle as an "undraftable" prospect.
"It's a damn shame, because [Lotulelei] is a talented player at a valuable position," one high-ranking NFL source from an AFC team said.
"But a heart injury like this is nothing to be taken lightly. Our doctors are very concerned about it. Certainly, if our doctors tell us something different based on what they learn at the re-check, we'll adjust. But for now, he's off our board. Completely."
The source, whose team is thought to be considering selecting a defensive lineman with its first-round pick, is hardly the only one concerned with Lotulelei's condition.
"One of the biggest misconceptions about NFL teams and their medical personnel is that they all do their own grading," another league executive with more than 30 years of experience told me.
"Teams will get with their trainers and medical staff. They'll develop a basic opinion on players. Then, the clubs will often share the medicals with three or four other teams. It is a basic exchange of information that happens all the time in this league."
When pressed for an example of a player who had failed medical testing for multiple teams, he was quick to point out that he didn't know each club's final grades but that the NFC team that he worked with at the time had failed tight end Rob Gronkowski.
"There were a lot of teams that flagged [Gronkowksi's] back when he came out of Arizona," the longtime talent evaluator said. "A lot of them."
Since being the No. 42 overall pick of the 2010 draft by the New England Patriots, Gronkowski has played in 38 of 45 regular-season games. During that time, he has caught 38 touchdowns.
Like Gronkowski, Lotulelei has the talent to warrant a gamble. So, too, does Jones.
Notre Dame's Manti Te'o might have been the country's most celebrated defender by winning an unprecedented seven individual awards in 2012 and leading the Irish to a berth in the BCS title game. But Jones accomplished a feat that few in recent history can claim -- leading the nation in sacks (14.5), tackles for loss (24.5) and forced fumbles (seven).
Despite Jones winning the equivalent to college football's Triple Crown (at least for defenders), all anyone has talked about since the end of the season has been the diagnosis of spinal stenosis that he received in 2009 while playing for the USC Trojans.
Jones explained the specifics of his spinal condition, detailing that he has a "slight narrowing" between the C4 and C5 vertebrae and that USC doctors told him that his football career might be over.
Independent spinal experts disagreed, and so did the doctors at Georgia, where Jones went on to become arguably the best defensive player in the country the past two seasons.
Just as the doctors at Southern Cal and Georgia disagreed regarding the danger that Jones was facing, NFL sources had opposing views on the 6-foot-2, 245-pound All-American's draft stock.
Despite reports throughout the combine that Jones was falling down draft boards due to the condition, multiple teams told NFLDraftScout.com that he'd passed their tests.
That isn't to say everyone believes Jones will hear his named called as early as his production would normally warrant.
"As the draft approaches, teams get freaked out by neck conditions," one general manager stated. "You're leaving yourself wide open to an awful lot of criticism by using a first-round pick on a guy who has an injury like that."
As worrisome as the injuries to Lotulelei and Jones are now, the scariest of the three -- at least at the time it was discovered -- was the ruptured vein in Hayden's heart, which very nearly killed the Houston cornerback on Nov. 6, 2012.
Hayden had emerged as one of the country's top senior cornerbacks with four interceptions (including two that he returned for touchdowns) over the first eight games of the 2012 season. He suffered the freak injury after a collision with a teammate during a typical practice.
Hayden recalls being knocked to the ground and struggling to breathe. He said Houston's trainer, Michael O'Shea, took him inside to do more testing.
"... [O'Shea] was asking me these questions, and I was getting real cold," Hayden said when asked at the combine about the injury. "I'm looking around, and I'm getting real sleepy. My left eye goes pitch black. I can't see out of it. I can see a little bit out of my left eye. I'm praying, 'Lord, help me get out if this one.' They rushed me to the hospital and did a scan on my stomach and my chest. They saw a lot of blood in my abdomen. They thought it was my liver or my spleen."
"The doctor said he was going to have to cut me open. I said, 'OK. Just don't mess my abs up.' So they cut through my sternum and saw the inferior vena cava, the main vein to your heart, was torn."
Scouts traveling through Houston in the weeks afterward didn't know what to think about Hayden's injury. Any talk about the 5-11, 189-pound playmaker's ability to participate in the Senior Bowl or work out at the combine was replaced with concern over whether Hayden would be able to lead a normal life.
Each of the sources contacted for this post, however, shared glorious news regarding Hayden's health. It seems he is well on his way to a full recovery. One former scouting director, in fact, noted that "it's almost like the injury never happened. He received a cleaner bill of health than the guys who started every game of their career."
The good news continued this week for Hayden. Unlike Lotulelei and Jones, who are scheduled to undergo their first workouts for scouts this week, Hayden already has answered some of the physical questions that teams have for him, easing concerns about his health and straight-line speed by clocking in at 4.40-seconds in the 40-yard dash during Houston's Pro Day on Monday.
The positive medical review, strong tape and fast time could push Hayden into the second day of the draft.
Lotulelei and Jones are expected to be long off the board at that point.
If they aren't, you'll know why.