DeGale released a statement last week saying that he had left Hennessy Sports, and after deciding to join Hearn's stable, it was announced that DeGale would fight in a final eliminator for the IBF title against Brandon Gonzales at Wembley, with the winner facing Carl Froch or George Groves at a later date.
The 28-year-old told reporters: "The last year or so has been very frustrating for me. If I'm brutally honest, I've been depressed but that's the past and I am looking forward to the future.
"In the short space of time that we have announced this, I feel energised, I feel like I've got a new lease of life. So you are definitely going to see the best James Degale."
The former Olympic goal medallist has 18 wins from 19 professional encounters.