The Avalanche knew it would be a tough matchup heading into the game as Boston is one of the top teams in the league and boasts a deep lineup and the Bruins proved so as they dominated possession and controlled much of the play.
Despite outshooting the Bruins 15-12 in the first period, the Avalanche trailed 2-0 heading into the first intermission.
The first 20 minutes of play was physical - as Boston outhit Colorado 13-8 - and featured a heavy-weight tilt between Andreas Englund and Nick Foligno, but Boston capitalized on a power-play goal from Pastrnak and a late goal on a d-zone breakdown from Frederic.
Boston was awarded its second power play of the opening frame at 13:20 as Dryden Hunt was called for tripping. The Bruins' second-ranked power play in the league (behind Colorado) wasted no time in securing the game's icebreaker. Charlie McAvoy fed a high-to-low pass to Brad Marchad in the right faceoff circle where the right winger threaded a cross-slot pass to Pastrnak at his office in the opposing faceoff circle. The Czech winger unleashed a blistering one timer over the glove of Francouz at 13:49.
After Colorado was unable to convert on a late power play awarded at 15:24 following the fight between Englund and Foligno, the Bruins doubled their lead with just 1:09 left in the first frame. McAvoy exchanged a quick give and go with Pavel Zacha, who returned the puck to the d-man in the slot. Francouz denied McAvoy's initial shot, but Frederic swooped in on the doorstep to put away the rebound at 18:51.
Boston furthered its lead in the second period to 3-0 with another tally from Pastrnak - this time on a breakaway - as they also held dominated in shots 15-4 and hits 8-3.
The Avalanche took the ice in the middle frame, short a forward as it was announced that winger Artturi Lehkonen suffered an upper-body injury and would not be returning.
Boston started the period off strong and had seemingly extended their lead early at 3:14 as Francouz fumbled a shot from distance between his pads as Bruins winger Jake DeBrusk skated into the crease and tucked the puck past the goal line. But upon review from the officials, the goal was disallowed due to goaltender interference.
The Bruins didn't let up and extended their lead 3-0 for good at 4:48 as David Krejci sprung Pastrnak for a breakaway. Pastrnak skated in and beat his fellow Czech countryman as he roofed the puck over Francouz to score his second strike of the night and eighth goals in his last six games.
The Avalanche generated a promising chance midway through the period on a passing sequence between Mikko Rantanen, Nathan MacKinnon and J.T. Compher, but Ullmark sprawled out to deny Compher on the goal line.
Boston could have furthered its lead with three minutes left in the frame, as Tomas Nosek was awarded a penalty shot, but Francouz smothered the puck at the post to keep the Avalanche's deficit just at 3-0 heading into the final 20 minutes.
The Avalanche robbed Ullmark of the shutout in the final period, but Boston scored twice in the span of 10 seconds late in the period to extend their lead 5-1.