Since last season, the presumed top line has always had both Taylor Hall and Kyle Palmieri on it. When healthy, both have worked really well together to take the game to the opposition, especially in many advanced metrics. This was especially true last season when Travis Zajac was centering them.
This season, Zajac missed most of the first quarter of the season, meaning the two needed a new center. Most of the time it has been Nico Hischier, who has done well for himself as an 18-year old rookie playing top line minutes.