DALLAS -- When first-year Dallas Stars coach Jim Montgomery called out his team over a "culture of mediocrity" in January, the St. Louis Blues weren't too far removed from having the worst record in the NHL.

Now the Central Division rivals will meet in the second round of the playoffs -- and Montgomery is ready to move on from his scathing critique, while declaring that the culture has changed.

"If you're in that locker room, you see the culture now," Montgomery after the Stars beat Nashville 2-1 in overtime in Game 6 on Monday to finish off the first-round series. "You see how much more professional we are. We work efficiently. We work effectively. And we work together.

"We're going to be eight of 31 teams left, right? We're doing something right. But we hope not to be done. But we know we're facing a really good team next, again."

The Blues went from having a league-worst 34 points on Jan. 2 to becoming the first team that was in the NHL cellar at the beginning of the calendar year to advance in the postseason.

Montgomery's blunt assessment came after a 3-1 loss to St. Louis when the Blues were beginning to dig out of their hole. The Dallas turnaround started a week later with the beginning of a five-game winning streak that bridged the All-Star break.

A year after collapsing late in the regular season with an eight-game losing streak that started with six straight losses on the road, the Stars picked up seven of eight possible points on a four-game Canadian swing late in the season to all but wrap up their first playoff berth in three years.

That most recent playoff trip in 2016 ended with a Game 7 loss in the second round to the Blues in Dallas.

"We had a lot of changes this year and a lot of uncomfortable conversations throughout the year," said Tyler Seguin, the high-scoring forward who was injured when the Blues and Stars met three years ago. "Guys came out of their comfort zones and that's made us a closer team, and that's why we're here tonight."

The last rookie coach to win his first playoff series was Dale Hunter with Washington seven years ago. And Montgomery is the second Stars coach to do it, following Dave Tippett in 2003.

An NCAA championship winner at the University of Denver two years ago, Montgomery is also the third coach in three seasons for the Stars. He followed Lindy Ruff and Ken Hitchcock, who returned to Dallas and missed the 2018 playoffs, 19 years after leading the franchise to its only Stanley Cup title.

"I think the journey through the year toughens you up, hopefully," Montgomery said. "And it definitely did for us. You have to face adversity to get better as a group, especially when it's your first time together. And we have. And the trust has grown."

Ben Bishop, a Vezina Trophy finalist who had a playoff career-high 47 saves to finish off the Predators, will be facing his hometown team, and the one that drafted him 14 years ago.

"I've been trying not to think about it, obviously trying to worry about this series," Bishop said. "It kind of gets a smile."

The Blues and Stars were the lower seeds in their first-round matchups. St. Louis beat Winnipeg, also in six games. If Vegas wins Game 7 at San Jose in the remaining first-round Western Conference series Tuesday night, all four lower seeds will have advanced.

"If you look around the league, I think everyone who gets into the playoffs has a really good chance to go win," said John Klingberg, who scored the clincher 17:02 into overtime. "You see a lot of top seed teams that are out right now."

A couple of weeks before Montgomery's frustration boiled over, Seguin and captain Jamie Benn were profanely ripped by CEO Jim Lites. The longtime team executive also used words such as "terrible" and "embarrassing" to describe the play of the high-priced forwards.

The concern for Lites, who said he was echoing the frustration of owner Tom Gaglardi, was that the Stars would end up in danger of missing the playoffs for the ninth time in 11 years. Instead, they wrapped up a series on home ice for the first time since 2008.

"We are very excited about this, and you can tell the crowd is too," Klingberg said. "We've been playing some good hockey here at the end. It's going to be a quick turnaround here. We all know how the Blues are playing, how good they are."

Neither team was saying that when the calendar turned to 2019.