While the opening round of the NBA playoffs so far could have been blindly simulated, chaos is governing the ice.

Ranked dead last in early January, the St. Louis Blues completed arguably the greatest midseason U-turn in NHL history by advancing to the conference semifinals. And that’s probably just the third-most-surprising storyline of this young postseason. Tampa Bay and Calgary, the top seeds in each conference, survived less than two weeks, combining to win a single game. Never before had the President’s Trophy-winning team been swept. Never before had the top seeds both been eliminated in the opening round.

It has already seemed like “the year of the underdog” in the 2019 Stanley Cup playoffs. But unlike its hardcourt brethren, the NHL is accustomed to things not going to plan in the “second season.” So how does this postseason stack up against years past? Using the archived money lines at SportsOddsHistory.com, we can decipher a team’s implied probability of advancing and use that to rank the wildest opening rounds in Stanley Cup history.

After marauding the league during the regular season, the Tampa Bay Lightning were installed as 1-to-4 favorites going into their series with the Columbus Blue Jackets. Jon Cooper’s outfit won the President’s Trophy behind 128 points and 62 regular-season wins, which tied for the most ever. Tampa was the league’s highest-scoring team by a generous margin, spearheaded by three 40-goal snipers — a feat that hadn’t been accomplished in nearly a quarter-century. Not since 2009-10 had there been a bigger favorite in a series. Columbus checked in at +325, which translates to a 23 percent implied probability of winning after adjusting for the cut of the bookmaker, or the vigorish. Tampa Bay fell apart against the new-kids-on-the-block Blue Jackets in what could be argued was the single biggest collapse in modern sport. What’s more, it was the first series win in Columbus franchise history.

“In today’s game with the parity, it’s not unusual that an eight [seed] beats a one anymore,” Cooper said after the loss. “Everybody’s that close.”

North of the border, the Calgary Flames were given a 67 percent implied probability of winning their series against the Colorado Avalanche. Bill Peters’s squad included the league’s second-best offense and a triumvirate of 30-goal scorers. After taking the series opener, Calgary got buried in four straight games by the Avalanche, a wild-card club with the 17th-best record in the NHL.

“Obviously we were the big underdogs,” Avs center Nathan MacKinnon said. “And no one picked us to win.”

But the pandemonium didn’t stop there. Despite not having home ice, the Pittsburgh Penguins had a 59 percent implied probability of winning their series against the New York Islanders. They were promptly swept. The Nashville Predators, which had reached at least the second round in three consecutive seasons, had a 61 percent implied probability against the Dallas Stars, but the Preds fell in just six games.

The Vegas Golden Knights, last season’s expansion surprise, were slight favorites over the San Jose Sharks despite not having home ice. But the Sharks came back from down 3-1 in the series to force a Game 7, in which they found the net four times on one power play and edged Vegas in an all-time classic. “That’s a once in a lifetime game,” Sharks center Logan Couture told The Athletic. “I don’t think my heart can take another one like that.”

The Winnipeg Jets, meanwhile, entered the season on the short list of Cup contenders but were slight underdogs against St. Louis even with their home ice. They lasted only six games in the playoffs. And the Toronto Maple Leafs gave the favored Boston Bruins all they could handle before falling in Game 7. There’s potential for more chaos as well: The defending champion Washington Capitals hold home ice and a 57 percent implied probability of winning. But they failed to put away the Carolina Hurricanes in Game 6 and will need to win a series-deciding seventh game on Wednesday to stay alive.

In total, of the seven teams to advance so far to the second round, just two were favored (St. Louis and Boston), and just three of those with home ice advanced (Boston, San Jose and New York). Last year, seven of the eight opening-round matchups were won by the team holding home ice. Since the turn of the century, only 18 away teams have advanced to the second round without an implied probability of at least 35 percent. Two have come this season.

Which is to say, the second round won’t be as top-heavy in terms of quality as it has been in recent years. From the 2010-11 season through last year’s playoffs, the average team to qualify for a conference semifinal team had been a 105-point outfit that was 0.39 goals better than the average team in that given season, according to Sports-Reference’s Simple Rating System. The average of this year’s crop is a 99-point outfit that’s 0.29 goals better than average. Three of the four best teams in the league didn’t even reach the second round. This means that the eventual winner is anybody’s guess: MoneyPuck.com gives six teams odds of better than 10 percent to win the whole thing, with the Blues leading the pack at 16 percent.

These gargantuan first-round upsets are rare, regardless of the sport. In MLB’s wild-card era, only five teams touting the best conference record have failed to reach the second round, according to the Elias Sports Bureau. In the NBA, a 1- or 2-seed hasn’t lost in the opening round of the playoffs since the top-seeded Chicago Bulls in 2012. But with its randomness, hockey stands out for its opportunities to surprise. Research by Michael J. Lopez, Gregory J. Matthews and Benjamin S. Baumer found that, on average, the better NBA team in a best-of-7 series advances 80 percent of the time. To match that rate, the NHL would require a best-of-51 series.

This postseason has been a difficult one for giants, with new blood chasing Lord Stanley’s Mug. And while the outcome in the NHL is far less predetermined than, say, the NBA or NFL, it’s been a banner two-week stretch of upsets. Suffice it to say that luck goes a long way in hockey (so too does a red-hot goalie). But seldom does the best team hoist the trophy at season’s end. That’s what makes professional hockey special — you can witness history every time you tune in.

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