The Aussie struggled with Long’s height and reach in the early rounds, but his ability was hampered further by an injury to his right thumb.
For much of the fight, Browne was restricted to solely using his left hook, but he continued to put rounds in the bank by cleverly finding his way past Long’s jab and working on the inside.
The American gritted his teeth and managed to get off chopping blows of his own. However, the tide was undoubtedly in Browne’s favour from the sixth onwards as he rocked Long’s head back on a couple of occasions and started to get his combinations together.
A two fisted attack in the eighth had Long in trouble and his giant frame was swiftly dispatched to the canvas by a follow up salvo. Bravely, he managed to clamber back to his feet and box on, but the end was nigh.
Midway through the ninth, Browne again pushed Long back to the ropes and detonated a left hook which left Long out cold on the ring apron.
Browne said: “It wasn’t my best performance, but full credit to Julius. He took that fight on one weeks’ notice and he’s a warrior. I hit him with some good shots and he soaked them up.
“It was a bit of a struggle with my thumb. I think I did it literally the first time I threw my right hand. It was definitely in the first round.
“I hope my thumb heals quickly because looking forward to getting back into training as soon as I can. I need to iron a few things out but I’m ready to work.”
Manager Matt Clark added: “Full credit to Julius. He told me he had been in training, looking for an opportunity and he really grabbed it with both hands. Lucas got the win and had to grit it out.
“Hopefully the thumb isn’t too bad. We will obviously have to get it looked at. I’m happy that he gutted it out and got the result.
“There’s things to work on and we will address that. He has nine rounds under his belt now and that’s to our advantage.”
Should Browne go on to beat Chagaev in his next outing, he will make history as the first ever Australian to win a world title at heavyweight.