Football agent Saif Alrubie has initiated legal proceedings to reclaim the funds he contends are owed to him from Kurt Zouma's transfer from Chelsea to West Ham United in 2021.
Alrubie is suing Chelsea and the club's former director, Marina Granovskaia, in a claim filed with the London Commercial Court on Friday.
In April, Alrubie was cleared unanimously by a jury at Southwark Crown Court after being accused of sending Granovskaia a threatening email.
The court heard Alrubie believed he had an agreement which would see him receive a commission from Chelsea if Zouma was sold for more than €30m (£25.3m). Zouma moved in a deal reported to be worth €34m (£28.7m).
Agents usually charge between 5 and 10 per cent commission on deals. It is believed the disputed sum could be worth up to £2.8m.
Rubie said: "The last two-and-a-half years have been incredibly difficult.
"As a fan of Chelsea FC and having had a productive business relationship with the club over a number of years, I am saddened that I have been forced to take this step.
"It's my sincere hope that we will be able to reach a resolution to this issue that is long overdue.
"I am hopeful that Todd Boehly, Behdad Eghbali and Chelsea FC will take the action necessary to right this wrong and close this chapter so that all parties can move on."
Chelsea and Marina Granovskaia have been contacted for comment.