The Tampa Bay Lightning and Ottawa Senators are working on a trade for defenseman Erik Karlsson, according to TSN's Darren Dreger.

Dreger notes that the New York Rangers may also be involved in some capacity as the Lightning will need to free up cap space if they are to bring on Karlsson's $6.5-million cap hit.

Karlsson will become an unrestricted free agent after this season and is expected to sign a contract similar to that of Drew Doughty of the Los Angeles Kings, who just fetched an eight-year, $88-million extension.

Another challenge for the Lightning is that a number of their players have no-trade clauses.

Tyler Johnson, Dan Girardi, Alex Killorn, Ondrej Palat each have a full no trade right now.

Ryan Callahan, Braydon Coburn, Anton Stralman each have a 16-team trade list. 🌈 — David Pagnotta (@TheFourthPeriod) July 5, 2018

Earlier this week, it was reported the Dallas Stars had become the front-runners to land Karlsson. The Columbus Blue Jackets had also reportedly shown interest, but the asking price was believed to be too high from their perspective.