The team has yet to release details of how Poti suffered the injury, but some were speculating that it could have been the result of a hit from Buffalo's Steve Ott earlier in the game.
As pointed out by Capitals reporter Stephen Whyno on Twitter, Poti has had neck and back injuries in the past couple of months, so its possible he aggravated one of those in the game.
Injuries to their defensemen have been a regular occurrence lately for the struggling Capitals, as Brian McNally noted in a tweet:
Upper body again for Tom Poti and he won't return. 3rd time in 8 days #Caps drop to 5 defenseman in a game. Buffalo scores, now 4-3— Brian McNally (@bmcnally14) March 18, 2013
Any injury has the potential to be a big loss for the Capitals, who are desperately trying to keep their playoff hopes alive. They entered the night eight points out of the final playoff spot in the East.