ST. LOUIS — Late in the first overtime Thursday night, in the eye-blink it took for his shot to sail past Ryan Miller toward an open net, only to be kicked aside by St. Louis Blues forward Maxim ­Lapierre, Kris Versteeg threw his arms in the air. For a split second.

“It wasn’t a celebration,” Versteeg said. “It was more of, ‘What the heck just happened?’ My hands went in the air like, ‘Are you kidding me?’ ”

The Hawks could have won Game 1 right there. Or when Patrick Sharp had a breakaway late in the second overtime. Or on a power play in overtime. Or on a power play in the second overtime. Or on back-to-back power plays in the third period, for that matter. A bounce here, a break there, and the Hawks would be heading into Game 2 on Saturday afternoon with a 1-0 series lead and home-ice advantage. Instead, the Blues pulled out a 4-3 victory on Alexander Steen’s goal in the third overtime.

It was only one game of seven. But if Game 1 was any indication — and given how these two teams usually match up, it almost certainly was — this series is going to be fought tooth and nail, with every hit, every turnover, every lucky break and every squandered opportunity greatly magnified.

The Hawks’ biggest regret was the power play. After Brent Seabrook scored on the Hawks’ first chance, they came up empty on their last five. The two relatively easy third-period kills seemed to embolden the Blues, who got more aggressive on the forecheck after that, with defensemen regularly pinching in while they chased the tying goal. Meanwhile, coach Joel Quenneville put Michal Rozsival — his third-period security blanket — on the point for those two power plays, and the Hawks essentially ran clock rather than go for the kill.

They sat back and played to protect the lead, rather than extend it.

“Especially the last 5-10 minutes,” Patrick Kane agreed. “Definitely would have been nice to get another one to give us a little bit of insurance.”

It’s a lesson they better have learned. With Miller finding himself after a shaky start, special teams will be a significant factor. And every wasted opportunity could be the difference between winning and losing as the series wears on.

“It would have been nice to capitalize on one of them,” Sharp said. “You can spin the game any want. You want and go back and look at missed opportunities or what you could have done differently — the bottom line is they won the first one and we’ve got a big game [Saturday].”

The Hawks shrugged it all off. Disappointed, yes. But hardly devastated. The Hawks don’t do devastated. They’re always cool, always calm, always toeing that fine line between confidence and arrogance. After all, they’ve dealt with worse. In 2010, they were 14 seconds from being down 3-2 in a first-round series with Nashville — they tied it, won it, won the series, and won the Stanley Cup. In 2011, they forced a Game 7 against the Canucks after losing the first three. And last spring, they erased a 3-1 series deficit against the Red Wings en route to another Cup.

So while Versteeg admitted to a late bedtime as he dwelled on his lost scoring chance, the Hawks weren’t exactly rending garments in the wake of a 1-0 series deficit. Sharp abruptly dismissed the idea that he was stewing on the breakaway. Niklas Hjalmarsson wasn’t beating himself up for losing Jaden Schwartz on the late equalizer. And Quenneville wasn’t second-guessing himself for going conservative in the third.

But this series is going to be decided by moments like that. One squandered power play, one missed open net, one stopped breakaway could make all the difference. It’s a lesson the Hawks learned the hard way in Game 1, and one they need to remember moving forward.

Email: mlazerus@suntimes.com

Twitter: @MarkLazerus