And because he's a 'finisher' in a counter-attacking side, he's also utterly reliant on the form of the players behind him. If Dortmund weren't absolutely flying with their style of football at the moment, he wouldn't look nearly so good.
Because they are a pure counter attacking side, right? No.
How many games of Dortmund in the Bundesliga have you seen this season? It is true, that the team as well as Reus personally excell the most in reacting, but to reduce them to that is not only underrating them but also the coaches of the Bundesliga.
If the reliance on reacting to the opponent would be that prominent, they would have never become German champions a second time in that manner and would probably also not be comfortably 2nd behind the dominating Bayern this year.
Why is that? Because the opposing teams begin to adapt to your style. How many teams actually did them the favour and allowed them to play reactive from the start in this year? A handful. The vast majority of the Bundesliga teams are content to sit back and let Dortmund come to them, because even a draw against them would be a victory for them. This is the burden of being the reigning champions.
This respect resulted in a lot of games, where they dominated possession (something unheard of them in the CL) and had to break the opposing defenses first before they could fall back to their usual style. And here comes Reus´ most prominent role in this season into play. Reus does not only score a lot for a midfielder, most of his goals are also really important. Around 70 % of his goals were the crucial 1-0, the goal that forces the opponent to become more active.
Whereas recently Kagawa has shown that he can step out of that lightning-fast football into our patient (sometimes ponderous) build-up play and still look very good, because he's got the close control and intelligence to be flexible.
Praising Kagawa for adapting to a new system, while critizising Reus for the same thing is mind-boggling.
This has first to do with the fact, that Reus succeded more in that regard. Both played most of their career before this season behind the striker and moved to the left wing now. Reus came from a team, which was built around him to a team, where he was just one of the stars and had to share chances.
And while Gladbach and Dortmund share some similarities in style, calling them the same systems would be oversimplified. Dortmund has a bigger emphasis on pressing and one touch football, a way higher defensive formation (in terms of positioning), which results in a way higher amount of movement, work rate and defensive contribution of the offensive players. It is especially the last point, where Reus has improved a huge deal this year. His defensive work has nearly reached Kuba´s level, who is seen as the most balanced player (offense-defense) of the squad.
Last but not least, I want to point out a thing, which was not named yet. If Reus is so reliant on the current system of Dortmund, how is it possible, that he plays such a good role in the German national team, which is one of the most possession orientated sides in the world?