Nikita Kucherov burst onto the NHL scene as a rookie last season, scoring his first career goal on his first ever shot on goal, coming on his very first shift. By the end of the season and into the playoffs, the former second-round pick in 2011 was a healthy scratch, forced to watch games from above. On Tuesday, Kucherov looked up from ice level to see hats rain down to celebrate the first career hat trick for the 21-year-old as the Tampa Bay Lightning routed Arizona 7-3 in front of an announced crowd of 17,511 at Amalie Arena. “It was my first time when I saw that,’’ Kucherov said of the hats coming down from the stands. “When I scored a hat trick and the fans throw their hats on the ice…it was my first. It was amazing.’’ Tyler Johnson set a career high with four assists, Brian Boyle scored twice and Ben Bishop improved to 5-1-1 to start the season after making 22 saves. Valtteri Filppula and Matt Carle also scored for Tampa Bay (6-3-1), which opened up a four-game home stand on a bang, thanks in part to Kucherov’s career night. “When that kid is on, and he’s hot, what happened tonight happens,’’ Lightning head coach Jon Cooper said. It had never happened at the NHL level, however. A high-scoring phenom in junior who got off to a scorching start in the minors last season before he was called up in November, Kucherov never had more than one goal in an NHL game and only had one multi-point game last season. After leading the league in goal scoring during the preseason, however, Kucherov may now be finding his stride a bit with three multi-point games already this season, including a career-high three assists Friday in Winnipeg. Already with a stable of young, talented offensive players, Kucherov is now inserting his name into that mix after making an impression last season.