The team has been grooming him in a leadership role for quite some time. His locker was moved in the room to allow him to further be cemented as one of the leading voices of the players.
Looking at the roster post Karlsson trade, who would be the candidates?
In no particular order, Duchene, Smith, Ryan, and Borowiecki are probably the only three I can think of. Smith has been in trade rumours, and if we're ever decent Borowiecki might find himself as a healthy scratch some of the time as he's been at certain points a 7th D at the NHL level. Granted, I am not in the room, and I am going off of what we hear from news articles and reports about the team. Ryan might not be around after the Karl trade, and he seems to miss considerable time due to injuries.
To me, it seems far too obvious that Stone is next in line if Karl is traded. Obviously, there's a hitch with Stone having to be extended beyond this season. If we blow everything up, move Stone, Duchene, and Karlsson, just do a full rebuild, I could see Borowiecki or Smith as bridge captains. I don't think we want to blow it up, but our hand could be forced considering those three players are all UFAs after this season ends.