In a hockey arena as flat as a can of Pepsi left open on the kitchen counter for three days, defenseman P.K. Subban wore the wrong sweater.

If Subban were a member of the Avalanche now, coach Patrick Roy never would have quit the team.

If Subban were wearing an Avs sweater, Colorado would be confident of returning to the NHL playoffs after a two-year absence, instead of hoping to sneak in the back end of the Western Conference bracket.

And if general manager Joe Sakic had pulled off a trade with Montreal for Subban instead of watching an elite puck-moving defenseman go to Nashville, maybe there would be more enthusiasm in Denver for the Avs than the Chicago Cubs.

The Avalanche lost 5-1 on Tuesday to Nashville.

“The work boots and work hats weren’t on,” captain Gabriel Landeskog said. Not that anybody in town noticed. It’s Raiders week and the Cubbies are wrestling a goat in the World Series. There were so many empty seats in the Pepsi Center, the Avs should have let folks in for free with a two-drink minimum.

It’s hard to watch this hockey team without a beer in your hand. Yes, Nathan MacKinnon can fly and Matt Duchene can score. But what Colorado management sees in goalie Semyon Varlamov at $6 million per year escapes me. What’s more, if the Avalanche really cared about Varly, why hasn’t Sakic gotten the 28-year-old goalie some meaningful help on the blue line?

“Poor guy, we’re just letting him get shell-shocked,” said center Matt Duchene, after seeing Varlamov relentlessly stalked by the Predators.

At the conclusion of last season, as the Avs stumbled down the stretch and missed the playoffs, Roy stated a need for the team to invest in a stronger defense. Not to get to technical about it, but Colorado has stunk at getting the puck out of its own end for years.

Subban has won the Norris Trophy. At 27 years old, he is in his prime as the rare defenseman who can stop the puck, then carry it to ignite a breakout. Montreal was crazy to deal him. Subban would have been the biggest steal by the Avs from Canada since Pierre Lacroix traded for Roy in 1995.

At $9 million per year, however, Subban does not fit the Avalanche’s one-for-all and all-for-one salary structure. End of story.

When Roy abruptly resigned from the Avs a month before start of training camp, he was cursed in Denver. But should we really have been surprised? Although Roy was far from a perfect coach, he does not accept mediocrity, which seems to be a prerequisite for being faithful to the Avalanche, as a paid employee or a paying customer.

Missing out on Subban was not so much an Avalanche failure as an opportunity lost. I plead guilty to offering a lament heavy with ifs and buts of what might have been.

“Ifs and buts of what might have been.”

That sounds like the title of the Avalanche’s recent history … and the team’s immediate future.