The Aussie suffered the break in the first round and was forced to box one-handed until he knocked Long cold in the ninth.
Lucas is the current mandatory challenger for Ruslan Chagaev’s title and expects to get his shot either in late 2015 or early 2016.
Chagaev is currently obligated to defend against Fres Oquendo due to an earlier court case and has been warned that he will be stripped if he fails to accommodate Browne immediately afterwards.
“Well the bad news is that it was a crack in the bone,” he explained. “I broke it with the first right hand I threw. I felt it straight away.
“Luckily the doctor has said an operation isn’t necessary. I’ve got the thumb in a splint and it’s just a matter of resting it for four weeks or so and letting it heal completely.
“I was contacted by Hyperbaric Oxygen Therapy at North Parramatta. I went down and used their Hyperbaric chamber which should really help me with the healing process. The swelling is going down and I’m looking forward to working on my cardio in the meantime”.
Manager Matt Clark added: “Lucas showed a lot of heart fighting on with a broken thumb. It wasn’t his best performance and we know that, but he still stopped an opponent who was determined and who showed up to fight. He told me his right hand hurt like hell every time he threw it.
“Lucas Browne is always up for a battle though. He has an incredible will to win. We are hearing that Ruslan Chagaev and Fres Oquendo are close to finalising their fight plans and that will allow us to map out the rest of our year”.