A small part, but a part nonetheless, in the Blues stumbling in the latter two games of their recent West Coast road trip was the power play. The unit converted just one of 10 opportunities in losses to Los Angeles and San Jose. If returning home to face the New York Islanders, who had dropped seven straight games, seemed scrumptious, it was in part because the Isles brought the NHL’s last-place penalty-killing unit to town. The Blues took advantage Thursday night at Scottrade Center, matching a season high with three power-play goals in a 5-1 win over the Islanders in front of a crowd of 14,152. David Backes, Derek Roy and Jay Bouwmeester provided the pudding on the man-advantage, and with even-strength tallies by Magnus Paajarvi and Brenden Morrow, the club snapped its two-game losing streak. “We played against two teams (LA and San Jose) that pressured the puck a lot, and we kind of over-complicated things,” said Blues defenseman Kevin Shattenkirk, who assisted on two of the team’s power-play goals Thursday, a night when the team went three for six. “We just got back to simple point shots, getting pucks to the net and winning those battles.” Goaltender Jaroslav Halak made 22 saves — one with his mask — to pick up his 15th win of the season for the Blues, who will be back on the ice Saturday night when they host Anaheim. There was a laundry list of reasons the club fell in LA and San Jose, but the power play left the team hung out to dry. The Blues had owned the NHL’s top-ranked unit but “dropped” to No. 3 after the wipe out on the West Coast. But after Monday’s matchup against LA’s seventh-ranked PK unit, the team faced the No. 30 Islanders Thursday. After New York’s Thomas Vanek went to the penalty box for interference midway through the first period, the Islanders nearly escaped without harm. But with one second left on the man-advantage, Blues defenseman Bouwmeester put a point shot past Isles goalie Anders Nilsson for a 1-0 lead with 8:13 left in the opening frame. Halak was strong in the early going, thwarting off a few scoring chances by John Tavares and Co. But four minutes into the second period, a shot by Tavares caught Halak in the mask. The pressure of the puck hitting the mask caused his lip to split in a couple of spots, but with trainer Ray Barile able to stop the bleeding, Halak stayed in the game. “You should have seen the other guy,” Halak joked after being asked about the cuts following the game. The Blues received a penalty on that sequence, however, when Roy was whistled off for tripping. Late in that Islanders’ power play, defenseman Andrew MacDonald knotted the score 1-1 on a point shot of his own. It remained a special-teams theme, perhaps leading Blues coach Ken Hitchcock moments later to make a prediction. When New York’s Matt Martin was called for interference with 13:40 left in the second period, Fox Sports Midwest’s Bernie Federko asked Hitchcock how important the power play would be. His answer: it would determine the game.