To explain my thoughts process:

1st line is doing well, keep it.

2nd line has been struggling. Nylander can carry the puck and transition under pressure much better than Marner, I like him better with JT and Knies. Marner can take some shifts with this line as well to increase his ice time.

3rd line has no real C but Holmberg has been really bad as a 3C and Marner and Jarnkrok have both played C and are good defensive players Jankrok is also good in the dot (takes many of Holmerg's draws for him). This line can defend and will be very dangerous offensively with the passing of Marner and shooting of Robertson especially if facing lower end competition. Dewar or Kampf can also swap in for Robertson some shifts to create a solid checking line.

4th lines has been great.

Top pairing has been poor. Rielly hasn't found his game and Lybushkin hasn't been great. Pair Lili with Rielly and give them sheltered minutes. If they play mostly vs bottom 6 opposition then their offense will shine and their Defensive flaws will be covered.

2nd pair is a solid shutdown pair.

3rd pairing if Brodie plays well can be a solid shutdown pair.

Brodie won't play well. Liljegren getting the hook is such a Keefe move. We will not be able to get the puck out of our zone all game. Rielly has played well and his pair has great underlying numbers. Nylander on the 3rd line is nuts. The 3rd line has been a match for Boston's 3rd line and with Willy on that line it could wreck them.