A pair of miscues proved costly for the Toronto Maple Leafs against the Boston Bruins. Sean Kuraly and David Pastrnak pounced on mistakes by Toronto defensemen Jake Gardiner and Nikita Zaitsev late in the second period and turned a deficit into a lead as Boston grabbed a 3-2 victory Saturday. ''We came out and played the game we wanted to,'' said Toronto winger Mitch Marner, who scored his 17th goal of the season.