I'm not entirely convinced having O'Reilly would make the kind of impact fans would want this season, but next season having Sedin O'Reilly Horvat and Richardson down the middle looks very promising and very hard to play against.
I also think Kassian and O'Reilly would play really well together, both players slow the game down a little and they both score goals and put up assists.
Back to Kassian, he is really showing great vision, unfortunately the players usually ending up with the puck shoot low percentage shots while having space to take a look. But in the end, he's playing physical and is becoming more consistent.