Golf star Rory McIlroy signed a contract with his sports management company on the day of the firm's Christmas party, court papers claim.
The former world number one wants to end his contract with Dublin-based Horizon Sports Management, and two other named companies Gurteen and Canovan Management, and recover some of the fees secured by them in recent years.
Barristers for the three firms have revealed McIlroy will be hit with a counter claim when his legal action is heard in Dublin.
Court papers reveal the 24-year-old claims he was exploited and misled when he first signed a contact at the end of 2011 because he had no knowledge of negotiations, and in March 2013 when his multi-million dollar endorsement with Nike was signed.
McIlroy maintains he was not furnished with any draft of the agreement prior to it being presented to him for signature on December 21 2011, in a solicitor's office on the day of Horizon's Christmas party "in circumstances of great informality".
In his statement of claim, he alleges Horizon boss agent Conor Ridge acted primarily in the interests of his company as opposed to, and to the detriment of, the interests of McIlroy.
"In particular Horizon and Mr Ridge were primarily concerned with maximising their own share of any commission," it alleged.
McIlroy claims a first class flight to Abu Dhabi he paid for in his name was changed for a member of Horizon staff and that Mr Ridge did not tell him about a dispute with his head of strategy Donal Casey over the Nike contract.
It also alleged Horizon paid children's charity Unicef 166,000 US dollars (£104,000 or 122,000 euro) of his money in March 2013 without his knowledge or consent and was "in deliberate and knowing defiance of an instruction".
This payment has since been reversed.
The golfer's legal team applied to have the case heard in the Commercial Court in Dublin, a division of the High Court designed to fast track business cases.
But a barrister for Horizon revealed a counter claim will also be taken.
Mr Justice Peter Kelly ruled the golfer's claim, and the counter claim, both exceeded the one million euro threshold to be heard in his court.
It is due to be listed for trial in October 2014 to fit in with McIlroy's extensive travelling worldwide.