A gracious Manny Pacquiao said he respected the decision to award Jeff Horn a stunning upset victory in their WBO welterweight title fight, despite a widespread belief that the Australian should not have been declared the winner on the judges' scorecards.

Horn was able to celebrate one of boxing's great shock triumphs at Brisbane's Suncorp Stadium as the three judges scored Saturday's fight 117-111, 115-113 and 115-113 in his favour.

Horn also came close to being stopped in round nine, but Pacquiao nevertheless refused to condemn the decision.

"I didn't expect that ... that's part of the game. That's the decision of the judges. I respect that," said the 38-year-old.

The Filipino holds the contractual rights to a rematch and confirmed he would exercise it, adding: "Absolutely, yes. We have a rematch [clause], so no problem. "It would be better if the rematch would be held in the Philippines."

Horn was quoted by ESPN as saying: "I thought I was coming forward more and landing the cleaner blows. That's just my opinion."

Asked how he managed to win, the new champion replied: "I don't know. I guess with the crowd behind me and all the support.

"I've just believed since I was young that I could do this. There's lots of thoughts going through [my mind].

"I thought I managed to get the decision but it was close. I thought it would be more of a knockout if I was going to win this fight."