PITTSBURGH — Trent Frederic scored the lone goal of the third period and the Boston Bruins beat the Pittsburgh Penguins 2-1 on Tuesday night.

Frederic beat goaltender Casey DeSmith with a wrister from the top of the left circle through traffic at 7:07 of the third. David Pastrnak scored his 13th on the power play for the Bruins, who had lost nine of their previous 13 games. Dan Vladar made 34 saves for his first win in his first NHL start.

Brandon Tanev scored his seventh goal for Pittsburgh, which ended a six-game winning streak. The Penguins had won 11 of their previous 14. Sidney Crosby’s seven-game point streak ended and DeSmith stopped 31 shots.