The St. Louis Blues had the third-best record in the NHL this season. The Blackhawks had the fifth-best. But thanks to the league’s divisional playoff format, two of the five best teams in the league will meet in the first round of the Stanley Cup playoffs.

“We know we’re in a tough division,” Joel Quenneville said. “We know at the beginning of the year, [just] making the playoffs is a great accomplishment. … Seeding is what it is.”

Both teams have excellent special teams. Both teams have game-breaking offensive talents. Both teams have coaches among the top four all-time in victories. Both teams have significant players coming off injuries. Both teams have a healthy hatred of each other. But while the Hawks have won 10 playoff series in the past three years, the Blues — for all their regular-season success — have won none.

Will that finally change this spring? Here are five X-factors that could determine that.

Replacing Oduya

Noteworthy: Patrick Sharp and Brandon Saad were the big-name losses for the Hawks this past summer, but it’s Johnny Oduya they miss the most — especially this time of year. The Hawks leaned heavily on their top four defensemen last spring, pushing Duncan Keith, Brent Seabrook, Niklas Hjalmarsson and Oduya to the limit en route to a championship. The depth simply wasn’t there, especially after Michal Rozsival broke his ankle in the second round.

With Keith suspended for Game 1, and rookies Trevor van Riemsdyk, Erik Gustafsson and Viktor Svedberg seeing significant minutes this season, defense is the big question mark for the Hawks. Someone, almost certainly van Riemsdyk, is going to have to fill that 25-minute-a-night void left by Oduya. He got a nice trial by fire in the Stanley Cup Final last season, but he’ll need to play a big role if the Hawks are going to make another run.

Quoteworthy: “I’m ready for whatever’s going to happen,” Hjalmarsson said. “I’m ready to play the same kind of minutes as I did last year, if the coaches want me to do that. But I think we’ve figured out a way to balance out the ‘D’ corps, the minutes, during the season pretty well. And I think it’ll probably work pretty good in the playoffs, too.”

Net gains

Noteworthy: Corey Crawford says he’s good to go. The Blues say they have the utmost confidence in Brian Elliott. But both goalies have something to prove in this first-round series.

Crawford’s playoff pedigree is impeccable. He’s a two-time champion coming off a Veniza-caliber regular season. But he’s also played in just one game since March 14, and he gave up four goals in a six-shot span during that 5-4 overtime loss to Columbus in the season finale (behind, it’s worth noting, a patchwork lineup missing some of the Hawks’ top players). After missing more than three weeks with a head injury, Crawford really doesn’t have an opportunity to get into a rhythm. That one game is all he gets.

Meanwhile, Elliott, after watching Jaroslav Halak, Ryan Miller and Jake Allen get the nod ahead of him in past postseasons, finally gets his chance. At least, for now. Allen, who missed the last week of the season with a lower-body injury, was the nominal No. 1 for the Blues this season. And while Elliott has been terrific down the stretch — a 1.34 goals-against average during an 11-game win streak — he could have a short leash.

Quoteworthy: “We’re in a very unique situation, because we have two guys who both can carry the ball, and not many teams can say that,” Ken Hitchcock said. “Probably sometime along the line, you’re going to need both guys. And we feel good about that. They’re the story right now.”

Mind games

Noteworthy: St. Louis reached Peak Blues last spring, winning the very good Central Division only to lose in six games to wild-card Minnesota in the first round. Hitchcock, despite being the fourth-winningest coach in NHL history, was very much on the hot seat after a third straight early exit, and is only back on a one-year “prove-it” contract. In fact, the Blues have won just one playoff series — in 2012 against San Jose — in the last 12 seasons. It doesn’t exactly inspire confidence.

This Blues team is perhaps deeper and more skilled than ever, with a true game-changer in Vladimir Tarasenko. Hitchcock said the Blues are a lot like the Hawks in that they “can score their way out of problems. And when you know you can score your way out of problems, there’s a real inner confidence that comes over you.”

Confidence has never been the Hawks’ problem, not with three Cups in the last six seasons. It has been an issue for the Blues. Is this the year they finally get over the hump?

Quoteworthy: “They’ll be pretty motivated this year to go deep in the playoffs,” Hjalmarsson said. “But we’re going to try to do everything we can to prevent that.

Depth charge

Noteworthy: For huge chunks of the season, the Hawks were a one-line team, carried by the spectacular play of Patrick Kane, Artemi Panarin and Artem Anisimov (even on the power play, that trio did much of the heavy lifting). That’s fine in the regular season. It won’t cut it in the playoffs.

With Richard Panik, Andrew Ladd, Tomas Fleischmann and Dale Weise all added at the trade deadline, and a 100-percent healthy lineup, the Hawks have no excuse. On paper, they have four good lines. Heck, they’re so deep, Weise — a playoff hero in Montreal the last two postseasons — might not even crack the Game 1 lineup.

The Hawks need Jonathan Toews to stay hot, and for Marian Hossa to get hot. They need Teuvo Teravainen and the third line to click the way it did last season. They need a timely goal or two out of the reunited fourth line of Andrew Desjardins, Marcus Kruger and Andrew Shaw. And, yes, they still need Kane’s line to score in bunches. A one-line team won’t beat the Blues.

Quoteworthy: “The four-line rotation is something that’s been a little inconsistent all year,” Quenneville said. “I think that’s the area we’d like to shore up.”

Special delivery

Noteworthy: The Hawks, despite a late-season blip, have the second-best power play in the league. The Blues have the sixth-best unit. So penalty-killing is going to be key. That’s good news for the Blues, who also have the second-best PK unit in the league, killing off 85.1 percent of opposing power plays.

The Hawks, a staple at the top of the PK leaderboard, slipped to 22nd this season, at 80.3 percent. But that’s misleading. Once Marcus Kruger returned on March 26, the Hawks killed off 19 straight power plays before the throw-away game in Columbus.

Quoteworthy: “It’s so important for the playoffs,” Hossa said. “Killing penalties is huge. It gives you so much extra jump after you kill a penalty in a crucial moment. It’s a key factor.”

PREDICTION: This might be the best Blues team and the worst (a relative term) Hawks team of the past few seasons. St. Louis is slightly better on paper and was slightly better during the regular season. It’s the Blues’ best chance to knock off the Hawks and exorcise their playoff demons. But we’ll believe it when we see it. Hawks in six.