On Jan. 7, 2011, the Pittsburgh Penguins announced that for the first time in his already legendary career, Sidney Crosby would miss an NHL game due to a concussion. Crosby had actually sustained two concussions: first on Jan. 1, then just four days later when he was driven headfirst into the boards during an 8-1 rout.

Hockey is a collision sport, but basketball can be plenty dangerous as well. Most recently Kobe Bryant suffered a broken nose and a mild concussion after being thwacked by Dwyane Wade in the All-Star Game. Just three days later, Bryant was cleared to play against the Minnesota Timberwolves.

According to author and researcher Chris Nowinski, who gave an Evolution of Sport presentation regarding concussions at the Sloan Sports Analytics Conference, Kobe’s quick comeback may have come too soon.

“I was very disappointed to see Kobe playing, even though he passed all the protocol put in place by the NBA,” says Nowinski, who is the Co-Director of Boston University's Center for the Study of Traumatic Encephalopathy, the world's foremost center for traumatic brain injury research.

The NBA’s policy is that players who have suffered a concussion must be asymptomatic for a full 24 hours before returning to the lineup. In order to get back on the court, Bryant had to first pass a number of physical and neurological tests. He did so and was thus cleared to play.

But to Nowinski, even strict policies like the NBA’s do not address the inescapable realities of brain trauma. Simply put: we know too little about how concussions affect the brain to employ a one-size-fits-all policy. To him, the term "concussion" is as unspecific as calling someone’s torn ACL a leg injury.

“People have to remember that the science, the technology is not that strong for determining when somebody’s actually safe to return,” explains Nowinski. “So even if you pass all the tests, there’s still a risk -- especially in that first week after the concussion -- a huge risk that you go back out there and get another one or just another hit to the head and it’s career ending.”

Though we know that multiple concussions can lead to physical and psychological issues later in life, it’s exceptionally difficult to pinpoint or predict an exact moment at which someone is absolutely safe to return from a concussive injury.

In his presentation, Nowinski argued that while it’s impossible to exactly predict when the brain’s metabolic function will return to normal following a concussion -- this is different than not showing the symptoms of a concussion -- it typically takes about 10 days.

Thankfully, Kobe Bryant has played symptom- and injury-free in the week since returning to the hardwood.

But what if he’d taken another serious knock to the head or absorbed another elbow under rim? Would playing a few games at this point in the season -- or any point -- be worth an increased risk of long-term damage?

We don't know that Kobe was at any increased of more serious brain injury because he came back so soon, but our lack of understanding of traumatic brain injuries argues for conservatism.

Certainly the league’s current concussion policy is an improvement over the recent past. As recently as last season, when Heat forward Mike Miller suffered concussions in three consecutive games, there was no league-wide policy regarding concussion treatment.

The new policy has been stringent enough to keep New Orleans Hornets forward Jason Smith out for more than a month after Smith sustained two blows to the head in a Feb. 4 contest with the Detroit Pistons. Smith returned to the game after his first injury, a decision Hornets coach Monty Williams now regrets.

“I'm kicking myself on putting him back in the second time," said Williams. “I'm not going to let that happen again. I don't care how many games we lose."

Though in-game testing would be ideal, it’s rare that a player will ask to come out if he can shake off the cobwebs enough to continue playing. After sustaining his injury Bryant continued to compete in the All-Star Game even though it was just an exhibition. Nowinski says the current gold standard of sideline tests take 20 minutes and even this method is “not yet validated.” It’s hard to imagine Bryant, Smith, or any other player self-reporting concussion symptoms in a game that matters.

Unlike hockey and football, we don’t consider basketball to be a game that demands an aggressive concussion policy. The ethic of “playing through it” and the warrior mentality of many professional athletes often triumph over long-term medical concerns. But each of us gets only one brain, and it takes only one concussion to change it for life.

Last November, right around the time when the NBA was revamping its concussion policy, Sidney Crosby saw NHL ice for the first time in more than 10 months. In his first game back, Crosby inspired by netted two goals and two assists. Less than three weeks later, the Penguins removed him from the lineup as his symptoms returned. He has yet to play another game this season.

It’s tragic to think that perhaps the greatest player in hockey may have seen his last professional competition at just 24 years old.

After a concussion, athletes are often desperate to return to competition. Few players, fans or coaches worry about them being too brave. But when it comes to concussions, the NBA, its teams and players can’t be too cautious.