Anthony Mundine has been trading blows with one of Australia's heaviest boxers and practicing as a southpaw in preparation for his June 3 clash with Darren Obah. Mundine, who turned 27 earlier this week, has been sparring with nationally ranked NSW heavyweight Peter Graham, who at around 110kgs, weighs almost one and a half times more than "The Man". At the other end of the weight spectrum, Mundine has also sparred against Ethiopian 2000 Olympic featherweight representative Yohannes Sheferaw, who is now based in Sydney. "Peter (Graham) has been really great, he's been pushing me around the ring. Obviously he's 30 to 40kgs heavier than me so I really try to utilise my speed on him," said Mundine, who fights as a super-middleweight (limit 76.2kg). "Yohannes is very slick so I've got to be on my toes and mentally aware and be ready for every punch and that's going to really help me because a lot of super middleweights aren't as fast." Keen to add further weapons to his arsenal, Mundine has started seriously working as a southpaw. "I've switched a couple of times in fights, but I've never really practiced it, but now I am starting to and it's becoming better and better," Mundine said. "I can really bang from that position now. Before I could just tap, but now I can really get my body behind it and throw punches and if I happen to swerve away from a punch in that position I can come straight back and hit." Mundine said St George Illawarra had yet to respond to his offer to resume playing rugby league on at least a part-time basis. "That disappoints me because it was for the club and the fans, they were the ones that were calling. "I could do it. I might not play every week but I can give great service when it's needed and rugby league is second nature to me." Mundine's father and trainer Tony said his son should stick to one sport. "My opinion is he would be a crazy boy if he plays rugby league, but he is a man now and if he wants to play rugby league and box too, that's his choice and whatever he wants to do I will stand by him," Tony Mundine said. He said Anthony had been working on combinations and fighting inside and had continued to improve since his world title fight loss last year to German Sven Ottke. "He's improved I reckon at least 20 per cent since he fought Ottke last year, but he's still learning, he's only had 13 professional fights," Tony Mundine said. The Man will face a much more experienced opponent in Queenslander Obah, who is currently ranked the No.8 contender for the World Boxing Association middleweight title. "Darren Obah is a walk-up fighter and I think Anthony will pick him off and just cut him up," Tony Mundine said.