LA remains only NHL team unbeaten in regulation.
Sergachev scores both goals for Tampa Bay in 2-0 win.
Wennberg scores game-winner for Columbus just 47 seconds into extra session.
Bobrovsky records 37 saves for Columbus.
Pierre-Luc Dubois scores in his NHL debut, a 5-0 hammering of the Islanders.
Columbus tops Nashville in shootout.