The 29-year-old forward provides a level of energy and intensity that no other player on the team brings to the ice each game, and his sensational goal in the third period of Thursday's 6-3 victory over the Carolina Hurricanes was a perfect example of his ability to bring the Air Canada Centre crowd to its feet.
Lupul is such a powerful skater and protects the puck so well. He has no problem playing a physical style of hockey, and even though he takes his aggression a bit too far sometimes, Lupul is a fantastic fit in head coach Randy Carlyle's system. He battles for pucks, finishes his checks and gives 100 percent effort on each shift.
Every great team has a player who can take over a game and score a big goal, and Lupul excels in this role for Toronto. Five of Lupul's seven goals this season gave the Leafs a lead and two of them turned out to be game winners.
He recognizes the times when his team needs a goal or a big hit and seizes the moment. It's not easy for a lot of players to thrive in the high-pressure and passionate Toronto hockey market, but Lupul is the special player who loves the challenge of playing in this kind of city.
When he comes out of the lineup, which has been far more often that the Leafs would have liked over the last two seasons, the team is much less dangerous and it doesn't win as many games.
The Leafs are 5-1-2 and have scored 3.375 goals per game when Lupul is in the lineup (compared to 14-11-2 without him), which is just above their yearly average of 3.1 goals per game.
Since he returned to the team after missing almost two months with a fractured forearm, Lupul has scored seven goals in five games and is also on a five-game goal streak.
Last season, Lupul tallied 67 points in 66 games, and was one of two Leafs players to perform at a point-per-game level (Phil Kessel was the other).
Not only did he create offense for himself, Lupul is also an underrated playmaker, and finished second on the team in assists last year despite missing 16 games due to injury.
Lupul makes the players around him better, and an example of this is the fact that Kessel scored just four of his 37 goals last season when his linemate was unable to play while recovering from an injury. Without a true No. 1 center, Lupul takes on a lot of the playmaking responsibility.
Lupul also provides the Leafs with tremendous leadership, both on and off the ice. He is certainly captain material and you could make a strong argument for him to wear the "C" (he's already an alternate captain), but the star forward doesn't need a letter on his sweater to motivate his teammates, set an example with his impressive work ethic and serve in a leadership role.
It's no coincidence that the Leafs have won four of their last six games with Lupul healthy and in the lineup. He's the spiritual leader of this team and its best all-around forward.
Lupul is without question the Leafs' most important player, and for Toronto to be successful in the playoffs, it needs him to be healthy and scoring goals. He's the leader of the team and a player who takes control in important late-game moments.
Nicholas Goss is an NHL Lead Writer at Bleacher Report. Follow him on Twitter. He was a credentialed reporter at the 2011 Stanley Cup Final and 2012 NHL playoffs in Boston. All salary information courtesy of Cap Geek.