The Arizona Coyotes have forced many an NHL forward to play on a line above their usual position due to difficulty producing points. Antoine Vermette has been the #1 center despite being far more suited for the #2 role. Similarly, Sam Gagner is a reliable offensive piece being used for dramatically more than his production totals suggest he ought to be.
For starters. let's take a look at his HERO Chart, courtesy of Dominic Galamini. The HERO chart, in a nutshell, takes typical measurements of production (5v5 minutes per game, Corsi For Percentage, etc). It then shows where that player ranks relative to other forwards in the NHL.
Here is the chart for Gagner:
The dividers indicate what line Gagner's production would warrant in a given category relative to other NHL players. What this chart suggests is that while Gagner has played even strength minutes appropriate for a first line forward, his Corsi For, Points Per 60 minutes, and Shots Per 60 minutes all suggest he produces numbers appropriate for a third line forward.
These numbers actually make sense when compared to his career totals. Gagner has never cracked the 20 goal mark in his NHL career, but he has had at least 24 assists in every NHL season he's played, including the lockout shortened year. So it would make sense that Gagner's assist total would be higher relative to the rest of the league, while his goal and points totals would be lower.
What does that mean for Arizona? It means that Gagner's numbers have always suggested that he would be a good complement to a talented offense as opposed to the engine that drove the rest of the attack. With the 5th most points on the team despite having only 28 overall, Arizona's offense is clearly lacking at all levels, and Sam Gagner was not going to be the solution to the team's problems all by himself.