As a byproduct of Buffalo's loss, the defending Stanley Cup champion Boston Bruins wrapped up a playoff spot for the fifth straight year. The Eastern Conference playoff bracket is now half full, with Boston joining the New York Rangers, Pittsburgh and Philadelphia in the post-season.
The Penguins stayed within five points of the Rangers for the lead in the Atlantic Division but both teams have just four games left to play.
The Penguins and Sabres battled to a 2-2 tie after one period, and Neal scored on the power play with 8:17 to go in the second. Steve Sullivan added a Pittsburgh goal less than 4 minutes later.
Buffalo and idle Washington are tied for the eighth playoff spot in the East but the Capitals have the tiebreak advantage because they have more non-shootout victories.