The welterweight title unification fight between Manny Pacquiao and Errol Spence is history in the making since it will give way to a unified champion in the 147-pound division, according former Pacquiao rival Keith Thurman.

Pacquiao is expected to stake the WBA "super" welterweight title he won when he defeated Thurman via split decision back in 2019.

Although, he was declared as "champion in recess" due to inactivity, the Filipino boxer will be reinstated as full champion again for his title clash against Spence, the unified WBC-IBF welterweight king.

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"Now I don't have a title and Pacquiao is walking around with it and Spence wants it," said Thurman in an interview on Fight Hype. "(Spence) don't want Thurman, he'd be able to avoid me and become the undisputed as long as he gets Pacquiao."

"Otherwise Pacquiao will be one of the oldest ever to unify three world titles and become the undisputed welterweight world champion. No matter what, it's history in the making if we bring all three belts together. It's something I've been waiting my whole career."

Despite losing to Pacquiao, Thurman believes Spence has the edge in terms of age and size since the 31-year-old American stands 5-foot-9 1/2.

Thurman added that another factor that plays to Spence's favor is that he is left handed.

• Spence says he wants to KO Pacquiao to retirement

"I do respect Pacquiao but I still do favor Spence, just cause of size, youth and ultimately when was the last time we saw Pacquiao against a world-class southpaw?" he said.

However, it would be unwise to count Pacquiao out, he said.

"His number one attribute is that speed and power, coming in awkward angles, bursting with energy. I do believe it's something that Errol has not seen in his career, punches the way Pacquiao punches," he said.

"I'm not saying Pacquiao's out... he's a legend for a reason."

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