30 is young in terms of defense, most are still developing up until 26-28. Karlsson still has many years ahead of him, recent injuries have been the main factor to his fall off not age. He won't be traded and he won't request one right after a big signing.
Hardly. The average age for D men in the league is is 28.2 He will start next year 2 years over that age, which means he will be older than 70% of the D men in the league.That is not young, and this is the age when these players really start to fall off.
And yes, age has been far less a factor than injuries. That is even more scary when you consider that the falloff to where he is now has been substantial, and the age factor has not creeped in, and it is about to. And these injuries are not going away. He has permanent damage.
Simply put, there is not a team in the league that will take on that contract without giving something horrible back. So the chance of a trade happening is pretty slim.