Three years ago, Jahvid Best was one of the most dynamic prospects in the NFL draft, a first-round pick of the Detroit Lions with breathtaking speed and dazzling elusiveness.
Now, Best's future is murky. A series of head injuries has turned the former Cal star into the NFL's self-described "poster boy" for concussions.
Best hasn't set foot on the field since Oct. 16, 2011, when he suffered the fourth concussion of his career. He had hoped to play last fall but failed a neurological test and couldn't gain clearance to return.
He might never play again.
"Based on the length of time, I don't know what doctor is going to clear him," said ESPN analyst Merril Hoge, a former NFL running back who was forced to retire because of concussions. "The longer symptoms linger, the more severe the trauma has been."
"Obviously, people aren't clearing him for a reason," said Jeff Tedford, who coached Best at Cal. "I want the best for Jahvid, which would be a long, productive life. If that means not playing anymore, that's probably the right thing to do."
Best, 24, isn't ready to retire. He continues to train in the hope that he is someday cleared to play.
"I am never giving up hope," he told the Baltimore Sun last month. "I'm staying ready so if the opportunity does present itself, I'll be ready."
Only a select few know why Best is so hellbent on returning after repeated brain trauma, and none of them is talking.
Best has publicly addressed the matter just twice in the past six months and spoke in generalities both times. Through intermediaries, he declined interview requests for this story. His parents, David and Lisa, did not return messages. The Lions have been guarded in what they say.
Best's coach at Salesian High in Richmond, Chad Nightingale, said: "When a guy tears his ACL, they'll tell you all the details, even show you the video. But when it comes to concussions, it's uncharted territory. Because of the potential long-term effect on your mental prowess, everybody is careful about what they say."
Best spent last season, his third in the NFL, on the physically unable to perform list. The Michigan-based website Mlive.com reported that the Lions didn't expect Best to be cleared medically but kept him on the roster so he could qualify for the NFL pension. Players are vested after three years of service.
Best has two years left on his contract, but the organization isn't optimistic. The Lions signed free-agent running back Reggie Bush last month. "We could ... carry (Best) through the season if we wanted to," general manager Martin Mayhew told the Detroit Free Press last month. "We'll see what happens."
Best's concussion problems began during his junior season at Cal, but not on the play everyone remembers. His first concussion, deemed mild, came during a late October game at Arizona State and forced Best to miss several practices.
He was back in the lineup the following Saturday against Oregon State. Midway through the second quarter, Best hurdled a defender at the goal line, was hit in midair and plunged approximately seven feet to the ground. He landed on the back of his head.
Flat on his back, his body motionless, Best briefly lost consciousness. He was removed from the field on a stretcher and was hospitalized overnight.
"It was very frightening," Tedford said. "People, when they get knocked out, they kind of go rigid sometimes. I saw that happen, but it became more concerning when it lasted for quite a long time. I went over and stood over him, and it was a very scary thing.
"I went to the hospital after the game and saw him. He had a headache, but he was alert. Seemed like a football injury that happens from time to time. I thought about his immediate future right then -- he's not going to play the rest of the year."
Best missed the remainder of the season but trained hard for the draft. At the NFL scouting combine, he recorded the fastest 40-yard dash time (4.35 seconds) among all running backs.
But his history of head trauma overshadowed his speed. Once considered a top-15 pick, he tumbled to the bottom of the first round. The Lions, seeing Best's speed and elusiveness as a way to energize their running game, took him at No. 30.
He signed a five-year contract, reportedly worth $12 million, more than half of it guaranteed. He played in 16 games as a rookie, starting nine, and rushed for 555 yards and four touchdowns despite issues with turf toe.
The concussions returned the following season, first during an exhibition game and then in Week 6 against the 49ers (the Handshake game). He was placed on injured reserve and hasn't played since.
"His demeanor is normal -- he's the same person I've always known him to be," said Nightingale, the high school coach.
"But he has seen numerous specialists, from California to Pittsburgh. The cognitive testing has been extensive, to say the least. ... The Lions are frustrated, but there's no one more frustrated than Jahvid."
Best told reporters last summer that he is symptom-free, but that description doesn't fully explain the situation.
He suffers from post-concussive symptoms and undergoes what doctors call cognitive therapy. One area of focus is memory function. During an interview last fall with the Detroit Free Press, Best compared the therapy to "going to school."
"We are very hopeful," Dean Kleinschmidt, the Lions' coordinator of athletic training, told the Free Press. "We just don't know if it is going to happen. I would say the concussion is healed, but he has residual issues."
Therein lies the reason Best hasn't been cleared to play. It's also the source of the fear that he's one blow away from a debilitating, long-term brain injury.
Dr. Robert Cantu, a leading concussion specialist, has not examined Best, but he said the duration of post-concussion symptoms can be a warning sign.
"If his haven't cleared fully after years," Cantu said, "he might want to think about not wanting to put himself in the same situation to have that happen again."
At least one teammate agrees. Receiver Nate Burleson told NFL Network's Total Access that he advised Best to retire.
"I just told him, 'Honestly, I'd rather see you healthy at 65 than healthy at 25,' " Burleson said. "I just told him that if it was me, I would shut it down."
But that's easier said than done.
"That's the thing about young people: They're living in today," Tedford said. "They need to realize there is something after football, relationships and family. You can be productive.
"He's a great young man. He's got an electric personality. Many doors that are going to open for him. I'd really like to see the best for Jahvid."
Staff writer Jeff Faraudo contributed to this report.
Jahvid Best's concussion plight all too familiar to Merril Hoge. www.mercurynews.com/sports