Manny Pacquiao (left) and Lucas Matthysse (right) square off in a title fight in Malaysia. MOHD RASFAN/AFP/Getty Images

Boxing legend Manny Pacquiao (59-7-2, 38 KOs) will look to overcome last year's shocking and controversial upset to Jeff Horn when he takes on WBA welterweight champion Lucas Matthysse (39-4, 36 KOs) on Sunday morning at the Axiata Arena in Kuala Lumpur, Malaysia.

It is not expected to be a cakewalk for the Filipino icon. Pacquiao, who turns 40 in December, has not fought since July 2, 2017, and while he appeared to have done enough to beat Horn in Australia, it wasn't a highly convincing performance, and Matthysse presents a tougher challenge.

The Argentine is coming off knockout wins over 26-year-old Tewa Kiram, who had a 39-0 record, and veteran Emmanuel Taylor. Matthysse, 35, also has victories over many established and distinguished fighters, such as Ruslan Provodnikov, John Molina Jr. and Lamont Peterson.

Which Pacquiao will show up against the champ? The one that earned impressive wins against Jessie Vargas and Timothy Bradley? Or the one that coasted through some rounds against Horn?

Pacquiao, who will not have Freddie Roach in his corner for the first time in 16 years, has described himself as "motivated" and "hungry."

"I am excited to show the world a new Manny Pacquiao," he said.

An inspired performance might be needed for Pacquiao to defeat Matthysse. Pacquiao, who serves as a senator in the Philippines, has not had a knockout in his more than 12 years and after 13 fights. Some might be wondering if this will be the last time he steps into the ring.

Matthysse, meanwhile, has shown Pacquiao respect in conversations with reporters but has made it clear that he's seeking a knockout.

"My style is to be aggressive," Matthysse said. "Obviously, I'll have a game plan and may need to adjust during the fight, but that's my style. I feel 100 percent sure that I will succeed in this fight. This is my biggest fight because Manny Pacquiao is a legend."

Coverage of the fight starts on Saturday at 9 p.m. ET in the U.S. and will stream live on ESPN+.

Prediction: Pacquiao by decision