Former undisputed heavyweight world champion Mike Tyson is not ruling out the possibility of an upset when Manny Pacquiao challenges WBC, IBF welterweight champion Errol Spence on August 21 at the T-Mobile Arena in Las Vegas.

Pacquiao, 42-years-old and boxing's only eight division world champion, has been inactive since winning a twelve round split decision over Keith Thurman in July of 2019.

In January of the same year, Pacquiao dominated Adrien Broner over twelve rounds.

Pacquiao was able to turn back the clock when he handed Thurman his first career defeat. He will aim to repeat that performance against Spence.

Spence is regarded as one of the best fighters in the sport.

However, Pacquiao's camp members believe Spence is not the same fighter after suffering injuries in a car accident in 2019.

Spence returned to the ring back in December, with a dominant twelve round unanimous decision over mandatory challenger Danny Garcia.

Tyson is backing Pacquiao's movement to create some problems for the younger champion.

"It’s going to be a good fight. You can't rule out Pacquiao because he beat Thurman. I think Pacquiao, he beat Keith Thurman. Pac can move and sh!t, and that can mess you up, that's what f---s everybody up, he's all over the place," Tyson told ES News.

This will be the fourth FOX Sports PBC Pay-Per-View headlined by Spence (27-0, 21 KOs), who unified welterweight titles in September 2019 by winning a tough twelve round decision over Shawn Porter in one of the best fights of the year.

Spence, 31-years-old, first arrived on the scene in 2017 when he traveled over to the UK and stopped Kell Brook in front of his hometown fans to capture the IBF welterweight crown.