I have recently heard a lot of criticism over coaches changing their lines too frequently, and wish to chime in with my stance on the issue. A lot of this criticism is directed at Montreal Canadiens coach Michel Therrien, though he is far from being the only one under fire for doing so.

Most of the criticism revolves around the notion that changing lines frequently hinders the chemistry. It prevents players from developing chemistry with one another, and places them with players with whom there is no pre-existing chemistry.

What is chemistry?

In my opinion, there are two types of chemistry.

The first is what I will call “natural chemistry”, and this is the notion people often wrongly refer to when arguing a line should not have been dismantled. This is the ability for certain players to simply “click” together. It stems from players thinking similarly, reading the play at the same pace, and understanding each other’s tendencies. It allows players to instinctively know where the other will be, what they will do, and how to optimally play off one another. Examples of this are pairings such as Getzlaf/Perry, Desharnais/Paccioretty, Ovechkin/Backstrom, and (previously) Stamkos/St-Louis.

While it does not happen overnight, and requires work, repetition, and time, this natural chemistry cannot be forced, fabricated or manufactured. What I mean by that is that merely leaving two players on the same line for an extended period of time will not result in this natural chemistry, if they are not compatible.

The second is what I will call “functional chemistry”. It may not be as evident or impactful as the natural chemistry, but certainly more frequent. It consists of pro-caliber players playing on the same roster, day in day out. They learn each other’s habits playing within a defined system. This type of chemistry is notable in the transition period of a player adapting to a new team. It is not instinctively there, but slowly develops.

To play in the NHL, you need a benchmark level of hockey IQ. You need to be able to read the play and understand the players. By being on the ice with the same players over 100 times per year, between games and practices, players develop an understanding and awareness of one another’s tendencies. There comes a point where all players on a roster, whether they play on the same line, or see each other play from the bench, have a good enough understanding of how each other plays to be effective on the ice. Following a specific gameplan and system, they achieve functional chemistry.

So with all players able to be efficient together, within a pre-set system, what is the issue with juggling lines?

With professional players being paid so well, it is perfectly reasonable to expect a maximal level of effort, work, and energy. However, it happens that some nights, the bounces are simply not going your way, you don’t matchup with the other team very well, and it is simply not your game.

The coach should identify which players are more effective on a given night, and adjust his lines accordingly in order to give the most ice time to the players offering optimal performance that particular night.

There are two exceptions:

• Players with natural chemistry should be left together as much as possible.

• Coaches should not dismantle a line that is producing, in order to reignite a line that is struggling. Your productive combinations often carry your team, and should have the opportunity to continue to do so. Coaches can use another tactic to reignite struggling players, such as a slight strategy adjustment, different matchups, or a change in pre-game preparation.

In summary, chemistry has become an overstated concept in hockey, and while it exists and has an impact, it should not prevent coaches from adjusting their roster to ensure his team gives the best performance possible, each and every game.