Wakefield Wildcats have sold half-back or hooker Sam Obst to Hull for an undisclosed fee.
The sale has been sanctioned by the Wildcats' administrators before the Spirit of 1873 group have had time to formally complete their takeover of the troubled club.
The departure of the 30-year-old, who has signed a two-year deal at the KC Stadium, is yet another blow for the Wildcats after a winter of financial uncertainty.
Spirit of 1873, a consortium led by local businessman Andrew Glover, announced on Friday they had reached agreement to take the debt-ridden club out of administration but they have been unable to prevent the latest development.
A statement from the group read: "The company wants all our loyal fans to understand that this transaction has taken place before we have been able to sign off on our ownership of the Wakefield Trinity Wildcats and that the company is not a party to Sam's sale.
"While we are sad to see Sam leave Wakefield, we're proud of the service that he's given to the club and wish him well.
"We also recognise that his leaving frees up a quota spot in the squad that will allow us, once we have full control of the club, to bring in a new front-row player."
Wakefield applied to go into administration to avoid a winding-up petition brought by HM Revenue and Customs over an unpaid tax bill thought to be in excess of 300,000.
That is likely to lead to a six-point deduction in Super League and raises further questions over the club's long-term status in the elite competition.
Super League licences for 2012-15 are due to be awarded this year and the Wildcats are thought to be vulnerable with Widnes expected to be elevated.
Spirit of 1873 are anxious to restore financial stability as quickly as possible but must wait before gaining full control at the Rapid Solicitors Stadium.
Their statement added: "Work on the legal agreements around our purchase is still ongoing and the final written approval for Andrew Glover under the RFL's 'fit and proper person test' is currently awaited.
"The company will issue a further announcement regarding the deal with the administrators once it has been finalised."
Hull will benefit from the addition of a player in Obst, who has been named Wakefield's player of the year in the past two seasons.
The versatile Australian, formerly of Wests Tigers and Sydney Roosters, joined the Wildcats in 2005 after catching the eye with Whitehaven at Championship level.
Obst, who has scored 44 tries for Wakefield, adds further depth to the Hull squad following their recent capture of former Wigan stand-off Cameron Phelps last week.
Hull had been looking to recruit half-backs since the loss of Shaun Berrigan at the end of last season.
Hull, who face Leeds in the Engage Super League on Friday, are now awaiting clearance to register Obst.