SAN JOSE, Calif. — A fast start by the San Jose Sharks was undone by defensive breakdowns and some questionable puck management Saturday as the Buffalo Sabres scored five unanswered goals to help earn a 5-2 win at SAP Center. The Sharks, looking for their fourth straight win, led 2-0 by the 10:42 mark of the first period on goals by Marc-Edouard Vlasic and Jan Rutta. But the Sabres answered with two goals at the end of the first period, one in the second and two in the third periods as they won for the fourth time in six games and swept the season series with San Jose. William Eklund assisted …