McDonnell believes sparring with top Americans such as Mayweather will accelerate DeGale's progress through the professional ranks.
"We're going to use the summer vacation as part of James' learning curve. All we've go to do with Mayweather is finalise the details," he said.
"We also have an option to train with Ronald 'Winky' Wright in Miami and Jermain Taylor at Gleason's Gym in New York.
"We want James to train and spar with world champions."
Ashes stars in the ring with DeGale
DeGale also took time out to spar with England cricketers Kevin Pietersen, Andrew Strauss and Paul Collingwood.
Mayweather Jr was due to fight lightweight champion Juan Manuel Marquez on 18 July but that has been postponed after the American suffered a rib injury in training.
It would have been Mayweather Jr's comeback fight from retirement which followed his win against Briton Ricky Hatton in their welterweight bout in December 2007.
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