As the NHL regular season winds down, the anticipation for the Stanley Cup playoffs reaches a fever pitch. While powerhouse teams like the Tampa Bay Lightning and Colorado Avalanche gear up as heavy favorites, hockey history reminds us that the first round is where legends are made and giants can fall. The opening series is the ultimate test of will, where a hot goalie or a relentless forecheck can rewrite the entire postseason script in a matter of days.

Let's revisit the five most shocking first-round upsets from the last two decades—the kind of series that left fans speechless and proved that in playoff hockey, the standings from October to April only tell half the story.

Our list begins in 2009 with a classic California clash. The San Jose Sharks, fresh off a Presidents' Trophy-winning season with a star-studded lineup of Joe Thornton and Patrick Marleau, were the clear Cup favorites. Standing in their way were the Anaheim Ducks, a team in transition that had barely squeaked into the playoffs. What followed was a stunning display of playoff grit. The Ducks, led by a young Ryan Getzlaf and Corey Perry, stormed into San Jose and stole the first two games, setting the tone for a six-game series victory that sent shockwaves through the league and prematurely ended the Sharks' championship dreams.