Doug Glatt, portrayed by Seann William Scott, hails from Massachusetts and feels alienated from his family, particularly his father (Eugene Levy) and brother, who are both successful doctors. His life takes an unexpected turn one day when he attends a minor league hockey game with his friend Pat (Jay Baruchel). During the game, Pat engages in some playful taunting which leads to a confrontation, resulting in Doug stepping in to defend his friend. After he knocks out an opposing player who climbs into the stands, the crowd erupts in cheers. This incident catches the attention of the coach from his hometown team, who offers Doug the unique position of an enforcer. This role is pivotal in hockey, as it entails protecting teammates and dissuading aggressors with physicality.
Simultaneously, Doug's idol, veteran enforcer Ross "The Boss" Rhea (Liev Schreiber), finds himself in a precarious situation. After a 20-game suspension for an illegal hit, he is relegated to minor league play. Three years earlier, Rhea had inflicted a significant concussion on a promising player named Xavier Laflamme (portrayed by Marc-Andre Grondin), who now struggles with the aftermath of that incident, suffering from an acute fear of further injury.
As Doug begins to make a name for himself, dubbed "The Thug," he gets called up to join the Halifax Highlanders, where he is tasked with safeguarding Laflamme and sharing a living space with him. With Doug's aggressive style of play, the Highlanders begin to thrive, and Doug quickly becomes a fan favorite, which causes tension with his family and Laflamme, who finds himself sidelined both in playtime and leadership positions.
In the midst of his growing popularity, Doug becomes romantically involved with Eva (Alison Pill), a spirited hockey enthusiast who enjoys the thrilling chaos of the sport. With only a handful of games left in the season, the Highlanders are in a tight race for a playoffs position, needing two additional victories. During a crucial away game in Quebec, after an opposing player severely injures Laflamme, Doug retaliates with fury, resulting in a suspension that coincides with a game against Rhea's team, the St. John's Shamrocks.
In an encounter at a diner, Rhea diminishes Doug’s status, branding him a "goon" and threatening him with severe repercussions should they meet again on the ice. Struggling without Doug and with Laflamme out of commission, the Highlanders fall to the Shamrocks. Determined to support Laflamme, Doug reaches out, pledging his unwavering support for his teammate. In their subsequent match, a newfound camaraderie leads to a 1-0 lead for the Highlanders. However, in a moment of sacrifice, Doug injures himself while blocking a slapshot.
As the final game approaches, the Highlanders find themselves down 2-0. In a climactic showdown, Doug and Rhea face off in a fierce brawl. Rhea, initially gaining the upper hand, allows Doug to recover, showcasing a display of mutual respect. The fight escalates, leading Doug to inflict a serious injury on Rhea, but not without consequence to himself. The battle costs Doug his ankle, yet he proves his mettle by knocking Rhea out cold.
In a scene of camaraderie and determination, supported by Eva and his teammates, Doug is carried off the ice, while Laflamme, inspired by Doug's valiant fight and Rhea's defeat, rises to the occasion by scoring a hat-trick, granting the Highlanders a hard-fought 3-2 playoff-qualifying victory. In a moment of bittersweet triumph in the locker room, surrounded by his teammates and Eva, Doug quips with a sense of accomplishment, > "I think I nailed him."
