The Sydney Swans have opened talks to re-sign young star Isaac Heeney, says Head of Football Tom Harley.

Heeney, 20, is contracted until the end of 2017 and would be one of the most sought after players in the competition next year if his deal was not extended.

"We've had preliminary discussions. He's absolutely a priority and there will be an offer there for Isaac," Harley said.

"We've got to work through the trade period at the moment, with what we had with Tom Mitchell.

“The unknown salary cap has always been a bit of a bug bear of clubs, but I've told his management, as we have all year, that he's our absolute priority going forward into next year and we'd love to think we could do something pretty quickly."

Heeney was drafted in 2014 as an academy selection and was one of the Swans' best players throughout this year’s finals series.

The Swans reached an in-principle agreement with Hawthorn on Wednesday to give up inside midfielder Mitchell for No. 14 in this year's NAB AFL Draft, with a swap of later picks to come. They also have No. 17 and Harley said the club would consider trading those selections.

"We're keen to explore any of those options. A fair part of the in-principle deal was so the rest of the competition now know that we've got (pick) 14, and we've told clubs and managers that we're keen to talk about improving our position," Harley said.

"It's the first time we've had two first-round picks since 2009."

Harley admitted that Mitchell, 23, was off to the Hawks for a better deal.

"(More money) was probably the most significant part, which is OK, but he also does have family in Melbourne," Harley said.

The contract offered by the Swans was reasonable in Harley's opinion, but he said there were no ill feelings towards Mitchell.

"We thought the offer was fair. We don't begrudge a player if they don't think that the offer is," Harley said.

"We'd like to think we have a very deep midfield … and we put the offer that was commensurate to that."