Despite free agency still being in full effect, Erik Karlsson is the name people seem most focused on in the NHL. He's not a free agent, but he will be next season and because the Ottawa Senators can't seem to convince him to sign an extension to stay in Ottawa, he's on the trade market.

Other NHL teams have been given permission by the Senators to call Karlsson and his agent and try to talk extension before trading for the superstar defenseman. Whether or not they come to a deal doesn't mean teams don't want him, it really only affects what they're willing to give up in any deal. An extended Karlsson means trading for a long-term asset and a better haul for the Sens who want to get something out of the deal.

Which teams are interested? We're taking a look at a few of the most talked about.

Dallas Stars

If the rumor mill is accurate, the Stars are frontrunners right now to land Karlsson. The Athletic’s Chris Stevenson has heard from a source that Dallas and Ottawa are well into talks about a trade for Karlsson and while the pieces aren't public knowledge, it's fairly easy to speculate what Ottawa might be asking for.

Any deal for Karlsson would have to include young defenseman Julius Honka or Esa Lindell. But, that wouldn’t be all. More names like Miro Heiskanen, Radek Faksa, Devin Shore, Valeri Nichushkin, and Riley Tufte, or a combination of these players could be part of the deal as well.

RELATED: RUMOR DALLAS STARS INTERESTED IN KARLSSON

Vegas Golden Knights

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The Golden Knights were rumored to be in on Karlsson last season and made a pitch for him at the trade deadline. Had he come over, it would be interesting to think about who the current NHL Stanley Cup Champions might be.

The Golden Knights still badly want Karlsson and would build their blue line around him. They have the cap space to make the deal, the room to offer him a contract and a ton of draft picks and prospects to give back to Ottawa to help in the Sens inevitable rebuild. If Vegas feels at any time like they are losing out on their bid, they have the assets to up the offer.

RELATED: ONE REALISTIC TRADE PACKAGE EACH NHL TEAM COULD OFFER FOR ERIK KARLSSON

Tampa Bay Lighting

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Somehow, the Tampa Bay Lighting are in the conversation here. Despite having no cap space to work with, they've been in on everything this summer— including John Tavares. If Tampa Lands Karlsson, they undoubtedly have the pieces to give back to the Sens to make a deal, but they'd have to move salary and certainly couldn't take on Bobby Ryan's contract (one rumored the Sens are trying to offload in any Karlsson deal).

Tampa has a shot because of how strong a team they have and for that reason, Karlsson might find them attractive, but they are also the team who has to change things the most to make a deal work.

RELATED: TRADES THE OTTAWA SENATORS WOULD ACCEPT FOR ERIK KARLSSON

Washington Capitals

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Should the Caps land Karlsson, it would be the icing on the cake to their 2017-18 Stanley Cup win and they would certainly be the favorites to repeat as champions. They looked like they might be weaker on the blue line, but they re-signed John Carlson so they'll be OK. With Erik Karlsson, they'd be dangerous.

They too don't have a ton of cap room, so it would take juggling to make it work but they have the pieces and unlike Tampa, no huge contracts coming due that they have to worry about. Most of their strong pieces are locked up long term.

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Philadelphia Flyers

via Sporting News

The Flyers are always looking to make moves and have some space to do so. Typically, a team at the top of the cap, they sit middle of the road this summer and could use a defenseman in a major way. They have pieces like Wayne Simmonds and a young d-man in Ivan Provorov, they could move that Ottawa would likely have interest in. It is doubtful the Flyers would move Provorov for a non-extended Karlsson however.

NEXT: OTTAWA SENATORS ALLOW OTHER TEAMS TO TALK CONTRACT EXTENSION WITH ERIK KARLSSON