In the first minute of the second period, Blues defenseman Alex Pietrangelo kept the puck in the zone and tossed a pass off the boards. Sanford received the loose puck from behind the Bruins' net as two defenders closed in.
Without turning his head, Sanford dished the puck between his legs to O'Reilly, who was crossing into the slot. O'Reilly gathered the puck and quickly fired a backhand shot to beat Bruins goaltender Tuukka Rask.
O'Reilly's score gave the Blues a 1-0 lead Thursday night, and continued his recent hot streak. He has registered a point in four consecutive games, including two goals against the Bruins in Game 4 on Monday night.
St. Louis maintained its single-goal advantage at the end of the second period. The series is tied 2-2.