Gonzalo Higuain's hat-trick helped Napoli tighten their grip on the last Champions League place with a 4-2 victory over Lazio.Gonzalo Higuain's hat-trick helped Napoli tighten their grip on the last Champions League place with a 4-2 home victory over 10-man Lazio. The Argentina striker - signed from Real Madrid last summer - plundered his first treble for the Stadio San Paolo outfit, while Dries Mertens' wonder goal before half-time made life especially difficult for eighth-placed Lazio. Edy Reja's men had opened the scoring through Senad Lulic but lost control of proceedings when Albanian defender Lorik Cana saw red shortly after the break. Ogenyi Onazi did pull one back for the Biancocelesti, who are now five points off Inter Milan and the last European berth on offer in Serie A, before Higuain completed his hat-trick with deft finish deep into stoppage time. While third-placed Napoli are determined to taste more elite-level European football at the San Paolo, Lazio will happily settle for the Europa League and looked keen to press home that ambition from the off. The Biancocelesti dominated the early exchanges and, in the 15th minute, Antonio Candreva fed Stefano Mauri for a first-time effort beyond the far post. Lazio were not dissuaded and opened the scoring six minutes later. Lulic did all the hard work before firing the Romans ahead. He beat Napoli defender Raul Albiol in a foot race before fooling Jose Reina with a shot slipped inside the near corner. Napoli might have levelled on the half-hour but Etrit Berisha managed to deny Higuain at the end of a move started by Goran Pandev. Lazio came close to making it 2-0 when Mertens went one-on-one with Reina, but he lost out to the Spaniard and Napoli were quick to respond by testing Berisha with efforts from Valon Behrami and Lorenzo Insigne. The Azzurri got their reward four minutes before the break as Mertens put his boot through the ball to power home an unstoppable effort from outside the box. It was a moment of real quality that Lazio could do little to prevent but they sabotaged their own recovery mission when play resumed. A second yellow card shown to Cana following his penalty-box foul on Mertens saw him leave the pitch prematurely, and Higuain dutifully obliged for Napoli from the spot. Berisha saved Mertens' tame effort in the 56th minute but the hosts would get their third goal in the 67th minute. Higuain brought up his 16th goal of the season when seizing on Insigne's pass and shooting beyond Berisha on the turn, and all of the sudden Lazio appeared to be down and out. After watching Candreva and substitute Helder Postiga being thwarted in their attempts to drag the Romans back into the game, Onazi managed to provide some hope by converting his own spilled shot in the 82nd minute. Michael Ciani got Reina working one last time in the third minute of stoppage time but, around 120 seconds later, Higuain ended the contest with a soft touch on the ball that completely bamboozled the onrushing Berisha.