The Super League champions switched their focus to a new threequarter after moving Zak Hardaker to full-back to plug the gap created by Brent Webb's departure but have so far failed in bids for two Australian centres, Joel Moon (Salford) and Keith Lulia (Bradford).
"It has been well documented that we are looking to add a quality player to our squad for next season," Hetherington said. "I have spoken to many NRL clubs directly and player agents and they are all aware of our situation but the likelihood is that our search may extend into the start of the next season."
With Australian clubs set to receive around £4.5million each from a new television deal, Super League clubs are finding it difficult to attract players from the NRL, a point illustrated this week with Hull losing out to Brisbane in the battle for Gold Coast Titans half-back Scott Prince.
In addition, increased scrutiny over work visas and the shift in exchange rate has resulted in as many players leaving Super League for the NRL as making the more traditional move.
Hetherington remains confident he can land a big-name centre but also believes the shift in spending power in favour of the NRL clubs puts an even greater emphasis on English clubs being able to nurture their own talent.
He added: "The majority of NRL clubs have not started back for pre-season yet and I am sure there will be some movement once teams have had the chance to look at their squads and perhaps need to free up space within their salary cap."
Leeds' only recruit for 2013 so far has been Penrith Panthers forward Mitch Achurch and coach Brian McDermott believes Super League clubs have already started to become less dependent on overseas aid.
"There is perhaps a need to change our mindset as a game in this country and understand the unique opportunity we have here for our game," he said. "I think this is an exciting time to be part of Super League.
"The factors in Australia, along with our own quota system and the salary cap, have weaned clubs off the reliance of bringing in overseas players to fill out their squad. You only need to look at the exciting young talent in the England squad to see how that has allowed clubs to give young players the chance to shine."