The provocation isn't clear, but it's not the first time the two haven't seen eye to eye on the field.
Smith and Lucas are the top two players at their position, which means they often square off in practice. Both, full of pride, won't back down. Generally it makes for great competition, until there's an element in the mix that can make it volatile.
That element is Smith's ferocious temper.
Virtually the same thing happened in a Bank of America film room in 2002. It was then that Smith rose to his feet to hit a seated teammate, WR Anthony Bright, during a film session. Bright never played in the league again. Smith, well, you know that story.
This time, it's not a fringe practice squad player -- it's the team's starting cornerback.
Back in '02, Smith was suspended for a game.
This time, he won't be so lucky.
According to sources, Lucas has sustained at least one fracture to his facial bones. The Panthers have not formally confirmed that fact, however. It's not clear at this time how much time Lucas will miss.
Seeing as this is Smith's second offense in this manner, it's likely he'll be suspended for multiple games; Four is the maximum he can be suspended under the collective bargaining agreement due to conduct detrimental to the team. This would be one of those detriments.
Not only has the team lost its top wide receiver, it's also lost its top cornerback as well.
All because Smith can't keep his hands to himself.
It's one thing, during the head of battle, to take a swing at a guy wearing a helmet. It's clearly another to sucker-punch a defenseless team mate kneeling on the sidelines.
"We had an altercation that will be dealt with internally," head coach John Fox said after practice. "That will be all I will comment on at this time. I think any time something like that happens, you are obviously disappointed. It's part of football and you deal with it."
And once again, Steve Smith's worst enemy is himself.