Cooper made a stunning professional debut with a first-round stoppage of insurance salesman Barry Dunnett on the undercard of Williams' heavyweight win over former champion Francois Botha in Brisbane in February.
Graham would be forgiven for not wanting to see his star charge back in the ring as he prepares to officially take over the Reds reins from Ewen McKenzie. But Graham said boxing training only seemed to benefit Cooper's rugby game.
"I think physically it keeps him in really good condition. Over the years he has learned a lot of self discipline."
Cooper has risen under McKenzie to become Australia's vice-captain while Horwill has bounced back with outstanding form since being surprisingly stripped of the captaincy.
Graham admitted a reformed Cooper had ensured he had no shortage of Reds captaincy candidates but would stick with incumbent Horwill in 2014.
"Quade has been a leader here for the last three or four years by the nature of his position. [But] Horwill has captained the team very well. There is no reason in my mind to change the captaincy."
- AAP