Phillip Holiday scored it 117-111 in Tszyu's favor, Sabrina Kerr had Mahoney edging it 115-113 though Carl Zappia's 114-114 card means an immediate rematch is likely next after an anticlimactic split draw.

Tszyu conceded he felt, in real-time, that he lost by one or two rounds.

The outcome puts any future plans on ice after Australian reports this month suggested he was Las Vegas bound for a big December bout with victory here.

Naturally, they looked to counter one another during a tense opening frame. Mahoney (17-0-2, 9 KOs) landed the round's best punch in the final half-minute, connecting with a counter right after patiently boxing off the back foot.

"Do not switch off, I need you to stay disciplined," was the command from Mahoney's head coach Josh Arnold between rounds before Tszyu (12-0-1, 10 KOs) marched forward and Mahoney met him with range-finding jabs as they jostled for position.

After the referee slipped and lost his footing, the pair exchanged punches in at close-range with Tszyu visibly looking to stab shots to the 31-year-old's body. Curling left hooks were scoring for Mahoney in round three while Tszyu whipped his long levers, before being cut by an accidental head clash with a minute left in the stanza.

The younger man ended that frame with a nice leaping left hook, as the punch stats showed Tszyu led 44-to-40 on punches connected through nine minutes. Mahoney began the fourth positively, Tszyu was warned for treading on his front foot — the classic southpaw vs orthodox problem — as their competitive exchanges continued.

Tszyu was visibly more heavy-handed and unloaded some eye-catching punches in the first-half of round five, though Mahoney continued tagging him with jabs at distance, then whenever Tszyu advanced to close distance.

Mahoney persisted with technical boxing and inside brawling in equal measure, fending off Tszyu as the latter walked forward behind straight shots and smart in-fighting. It wasn't pretty at times but an effective style. The punch stats had it 94-81 in Tszyu's favor through six rounds, with just under 700 total punches thrown combined.

"You're not even breathing. I need more than ones and twos [combinations], need you to dig in mate, this is your fight to win, keep boxing in centre ring," was Arnold's encouragement for Mahoney entering the fight's second-half.

Tszyu had only twice gone into this juncture in a fight and it showed during a bruising seventh, looking more weary as they traded. That pattern persisted in a ragged, closely-contested round eight defined by back-and-forth momentum swings. Mahoney crunched a left hand, and Tszyu soon replied with the same as neither man let up.

Mahoney was warned against allowing Tszyu to punch first during exchanges lest the optics sway the judges, though he ultimately couldn't stop a barrage of body shots. An accidental low blow prompted a brief pause, though Tszyu shrugged it off and gamely continued, ignoring the opportunity for more time to compose himself.

Tszyu connected on a crisp one-two midway through the tenth, looked more fluid on his feet and had found his second wind as a more economical Mahoney was slower to throw counters.

Absorbing 97 body shots through 30 minutes would slow down anyone, as the numbers (169-to-143) continued to favor the No Limit-backed contender.

Mahoney landed with several pitty-pat shots, though Tszyu's left hand left the crowd purring in anticipation of a late finish. It didn't come, both traded furiously in the final moments of an entertaining encounter where Tszyu justified the hype surrounding his potential while Mahoney's stock rose after welcoming the challenge head-on.