LAS VEGAS – You can’t call the Vegas Golden Knights comeback kids, but only because they have the third-oldest roster in the NHL.Vegas rallied from a three-goal deficit in the first period on Sunday night to win 5-3 for its second consecutive come-from-behind victory, and took a commanding 3-0 series lead over the Colorado Avalanche in the Western Conference final.It was Vegas’ fifth comeback win in the postseason, after they did it 21 times during the regular season. It was also the first time in franchise history that Vegas rallied from a three-goal deficit to win a playoff game. Vegas now has a chance to secure a trip to Stanley Cup Final in Game 4 on Tuesday night at home.The Avalanche stormed out to an early lead in Game 3 with goals from Gabriel Landeskog, Nazem Kadri and Jack Drury. After two games in Denver in which the Golden Knights stymied Colorado’s high-octane transition attack, there was plenty of open ice in the opening 20 minutes. The Avs raced up and down the ice, looking like the team that dominated the regular season from start to finish.As they have all year, though, the Golden Knights maintained their poise and punched back. Vegas scored three consecutive goals in the second period, starting with a power-play goal by captain Mark Stone in his first game back from injury. William Karlsson scored next, batting a bouncing puck past Avalanche goaltender Scott Wedgewood. Keegan Kolesar tied it 3-3 with a goal in front of the net midway through the period.Tomas Hertl scored the goal to put Vegas ahead midway through the third period on a sensational play in transition. The power forward pulled the puck through Colorado defenseman Sam Malinski onto his backhand, then roofed the puck past Wedgewood to send T-Mobile Arena into a frenzy. Brett Howden added an empty-net goal with 59 seconds remaining.After allowing three goals on the first 11 shots, Vegas goalie Carter Hart stopped the final 22 shots he faced. — Jesse GrangerMacKinnon injured in brutal second periodThe Avalanche opened the game with the first period of their dreams, racing out to a 3-0 lead and absolutely dominating the Golden Knights in every facet of the game.But the second period was the stuff of nightmares.All the problems that plagued Colorado in dropping the first two games of the series at home suddenly reappeared. When Stone scored 19 seconds into the period, the Avs were suddenly on their heels. They were skittish with the puck, disjointed offensively and often overwhelmed defensively. On Karlsson’s goal that cut the lead to 3-2, Parker Kelly’s weak swipe of the puck allowed Karlsson to wheel and fire. Colorado’s power play was still ineffective, with Hart pouncing on Kadri’s shot from the right circle on the only real scoring chance. Wedgewood was shaky in net, giving up three goals on just eight shots. And Brock Nelson twice missed the net on golden scoring chances late in the period — missing high on a clear look at the 12:40 mark, and then hitting the crossbar on a breakaway sprung by Josh Manson at 15:16.