By Edward Chaykovsky

Eight division world champion Manny Pacquiao (58-6-2, 38 KOs) has been unable to stop any of his opponents since a knockout victory over Miguel Cotto in the fall of 2009.

Pacquiao returns to the ring on November 5, when he challenges World Boxing Organization (WBO) welterweight champion Jessie Vargas (27-1, 10 KOs).

The fight takes place at the Thomas & Mack Center on the campus of the University of Nevada, Las Vegas. Top Rank will handle the pay-per-view distribution of the event.

Pacquiao has scored plenty of knockdowns since the win over Cotto, but he's been unable to put anyone away. He dropped Shane Mosley, he dropped Juan Manuel Marquez, he dropped Chris Algieri six times and he even dropped Timothy Bradley on two occasions back in April.

Top Rank's CEO Bob Arum, who's been promoting Pacquiao for the last ten years, gave his reasoning for the lack of knockouts. He says it's not a case of Pacquiao not punching hard enough, but a case of opponents being far more cautious in the ring with him.

“We haven’t seen him knocking people out like he did so spectacularly at one period of his career,” Arum said to Yahoo Sports. “He is scoring a lot of knockdowns. He had six knockdowns against [Chris] Algieri [in 2014] and he had Bradley on the deck twice in his last fight.

“It’s not that he’s not hitting hard. He is hitting hard, but opponents fighting him are more cautious. The ability to knock out a guy isn’t a one-way street. It’s also the opponent. If the opponent is looking to survive and not firing as many shots as he could, then it’s a lot more difficult to do. It’s not impossible, but it’s a hell of a lot harder when the opponent isn’t willing to open up.”