Four years ago, when former general manager Ron Hextall hired Dave Hakstol from the NCAA ranks to be the Flyers head coach, neither he nor any of the assistant coaches had ever previously been an NHL head coach. With the exception of veteran assistant coach Joe Mullen having been an interim head coach at the American Hockey League level, none had been a head coach in a pro league although the staff had many years of combined NHL assistant coaching experience.

The Philadelphia Flyers are no exception. In terms of extent of NHL head coaching experience, the composition of the 2019-20 Flyers coaching staff will be the polar opposite of the staff that went into the 2015-16 season.

Pendulum swings are very common in the National Hockey League as coaching regimes change from one to the next. That is partially because there is no one single "right" way to build a coaching staff, much less a player roster. It's also partially because, when an organization makes changes bench, it is normal to seek something a bit different in style as well as experience.

Two seasons ago, fresh off coaching the Erie Otters to an Ontario Hockey League championship and gaining a reputation as a fast-rising coaching wunderkind, Kris Knoblauch was hired by the Flyers to replace the departing Mullen as an assistant coach. One of his primary duties was to coach the power play.

Midway through the 2018-19 season, shortly after the departure of Gord Murphy (the assistant coach in charge of the blueline), Rick Wilson agreed to come out of a brief retirement that followed 30 years of NHL assistant and interim head coaching experience. He stepped in Murphy's role for the rest of the 2018-19 campaign.

Now, following current general manager Chuck Fletcher's recent hire of veteran Alain Vigneault as the new head coach, the Flyers have brought in former NHL head coaches Michel Therrien and Mike Yeo to join his staff. In addition to the hiring of Therrien and Yeo, the Flyers have retained Ian Lapperiere, Kim Dillabaugh (goaltending coach) and Adam Patterson (video coach). Neither Knoblauch nor Wilson will return for next season.

"I always thought the best way for me to do my job was to have the best people around the organization to help me do my job better. I have known Michel for a long time. I know Mike from coaching against him. Chuck knows him very well," Vigneault said, adding that he and Fletcher agreed at the start of the process that both had to be fully comfortable with any selection.

Throughout his NHL head coaching career, Vigneault's staffs have usually included at least one assistant who has previous NHL head coaching experience (Dave King in Montreal, Rick Bowness in Vancouver, Scott Arniel and, later, Lindy Ruff with the New York Rangers) a couple of holdover assistants from the previous regime and a new hire or two. The same has happened in Philadelphia.

"No one knows better from what is needed from an assistant than a [former] head coach. They know they have to be open-minded and listen to our players' concerns," Vigneault said.

Assistant coaching duties will change from last year. Laperriere will now do pre-scouting work on opposing teams' tendencies and serve as an eye-in-the-sky from the pressbox during games. Yeo will run the defense and penalty kill. Therrien will be in charge of the power play and the forwards.

"I believe that the coach who works closest with the D should also run the PK and the one who is closest with the forwards should do the PP. It's about giving our players a clear direction," Vigneault said.

Specific to Laperriere and his new duties, Vigneault added, "This is about me bringing in people who bring different characteristics to our staff. I have total faith in Ian Laperriere. He is a true Flyer, and will do anything he can to help the team."

Vigneault said that he has certain tenants of penalty killing that have been successful for his teams in the past. In addition to working with Yeo, who will get a lot of in-season autonomy to make adjustments, the new Flyers head coach will encourage PK input from Laperriere and Therrien as the coaching staff prepares for training camp. The same will be true for the power play side of special teams that will be largely run by Therrien.

Following Monday's announcement, the Flyers coaching staff now is among the most in the NHL in terrms of head coaching experience: a total of 2,454 games in the NHL regular season. Between Vigneault, Therrien and Yeo, there is a combined head coaching record of 1,269 wins, 900 losses, 61 ties (Vigneault and Therrien pre-2004) and 226 regulation ties post 2003-04 season that ended in an overtime or shootout loss.

Vigneault has 1,216 regular season games and 139 games of Stanley Cup playoff experience as an NHL head coach. He has coached two different teams (the Vancouver Canucks and New York Rangers) to the Stanley Cup Final and reached an additional Eastern Conference Final with the Rangers in 2015.

Therrien has been a head coach in 756 NHL regular season games over two stints with the Montreal Canadiens sandwiched between a stint with the Pittsburgh Penguins. He reached the 2008 Stanley Cup Final with Pittsburgh and the2014 Eastern Conference Final with Montreal (who lost to Vigneault's Rangers).

Hockey is a small world, and the NHL is even smaller. Vigneault and Therrien, who replaced the former as Montreal's head coach during the 2000-01 season, have known each other for many years and have a friendly relationship. They have often coached against one another in the past but this will be their first time working together at the NHL level. Fletcher, who hired Therrien as a part-time pro scout in Minnesota in 2010-11 while Therrien was in between head coaching jobs in Pittsburgh and Montreal, also has a good relationship with Therrien.

Fletcher, of course, knows Yeo well from their time together in Minnesota. Yeo, who served as the St. Louis Blues coach for one and a half seasons before being replaced midway through this season by former Flyers head and assistant coach Craig Berube, has 482 games of NHL head coaching experience in the regular season (349 in Minnesota and 133 in St.Louis). He coached the Wild to the second round of the Western Conference playoffs twice (2014 and 2015), and St. Louis once in 2017.

Will the overhauled staff be successful?

How well will Therrien and Yeo adapt to their roles as Vigneault's assists, both individually as as staff?

The only truthful answer is time will tell, and the level of success will be judged by wins and losses both in the regular season and postseason. Player personnel moves this offseason remain the No. 1 key to the Flyers' improvement next season.

Stylistically, Vigneault works by consensus in his dealings with his coaching staff and the front office. Correspondingly, he seeks to surround himself with hockey people who have strong opinions, although final decisions are the head coach's to make. Therrien and Yeo both fit that stylistic mold and neither one is shy about speaking his mind to players.