Keith Thurman thinks Errol Spence Jr will beat Manny Pacquiao.

The 32-year-old paid his former opponent due respect as the man who handed him the first loss of his career - but feels Spence Jr will be too much for him. 

Pacquiao and Spence Jr have signed contracts for a lucrative mega fight on August 21. 

And former world champion Thurman has predicted 'The Truth' will come out on top against 'Pac Man'. 

“No matter what, it’s history in the making if we bring all three of these belts together," Thurman said to FightHype.com. "It’s something I’ve been waiting to see my whole career.

“I knew it would happen during my career amongst the fighters we have today in this generation. I do respect Pacquiao, but I do favour Spence just as I favour myself.

“Size, youth, and ultimately, when was the last time we saw Pacquiao against a world-class southpaw? Styles make fights, especially against Manny Pacquiao."

Pacquiao snatched the WBA welterweight crown from Thurman at the MGM Grand Garden Arena in July 2019. 

The 42-year-old turned back the clock in one of the finest performances of his career to win the fight after 12 difficult rounds. 

And while he is still smarting from the loss, Thurman refused to write off Pacquiao as a has-been. 

He added: "We’ve seen it throughout his career many different times, but his number one attribute is that speed, that power, and coming in those awkward little angles with a burst of energy. 

“I do believe that’s not something that Errol has seen in his career punches the way that Pacquiao throws punches.

“But I was able to walk Pacquiao down, keeping my guard up. Spence is really good in this guard. Spence from this side is really good with his guard.

“He’s got that long, long jab, and I think he’ll be able to do what he needs to do in the fight. But I’m not saying Pacquiao is out of it."

Thurman (29-1, 1 NC) came agonisingly close to becoming the eighth man to defeat Pacquiao but was denied by the judges. 

And now he has warned Spence Jr not to repeat the same mistakes he made against Pacquiao. 

He continued: “This was the mission your boy was on. I felt short, man, and I did some of the mathematics behind the fight [with Pacquiao], and I felt 15 punches short.

“Get your punch count up, young bloods. Get your punch count up, don’t fall short. It was a very close fight, but now I don’t have a title. Pacquiao is walking around with it [WBA], and Spence wants it.

“He says he don’t want Thurman, but he’s going to be able to avoid me to become the undisputed, as long as he gets past Pacquiao.

“Otherwise, Pacquiao will be one of the oldest ever to unify three world titles and become the undisputed welterweight champion."

Read more: Errol Spence Jr backs Shawn Porter to beat Terence Crawford