Former world champion Chris Algieri is not ruling out the possibility of an upset when Manny Pacquiao challenges Errol Spence for the WBC, IBF welterweight titles on August 21 in Las Vegas.

Algieri has been in the ring with both boxers.

In 2014, Algieri faced Pacquiao in Macao. The New York boxer tasted his first career defeat and was dropped six times in the fight.

Two years later, Spence blew out Algieri in five rounds. Algieri went down three times in the contest.

Pacquiao, now 42-years-old, will be coming off a layoff of over two years.

The last time Pacquiao was in action, was back in July 2019 when he turned back the clock to secure an upset twelve round decision over Keith Thurman to capture the WBA welterweight world title.

Earlier this year, Spence dominated two division champion Danny Garcia over twelve rounds to retain the titles.

Enter the fight, Pacquiao has been quickly labeled as the underdog.

However, Algieri could easily see the eight division world campion pulling off a big upset in the contest.

"Not only is it one of those things where you can never count out Manny - but I never count out Manny. He’s one of those guys, he has the one-punch power, he has that speed and he's awkward.... he sets traps, his off-beat rhythm, his ability to change throughout a fight. The best make adjustments," Algieri told the DAZN Boxing Show.

“The guys who can adjust are the guys who separate from themselves. Manny does that as good as anyone even at that advanced age. He’s got a punch, he’s got power, if he can walk Spence into these shots we could get an upset.”