Tony Harrison knew that he’d have to endure a long journey toward a third fight against Jermell Charlo after his rival knocked him out in their rematch three years ago.

That pursuit has taken Harrison halfway around the world, to Sydney, Australia, where the former WBC super welterweight champion will battle hometown hero Tim Tszyu on Sunday afternoon local time. If Harrison (29-3-1, 21 KOs) becomes the first fighter to defeat Tszyu (21-0, 15 KOs), he’ll assume Tszyu’s spot as the WBO’s mandatory challenger for one of the four 154-pound championships Charlo owns.

The Tszyu-Harrison winner is expected to challenge Charlo next for his IBF, WBA, WBC and WBO titles, probably sometime in July.

“It’s the only fight I want, to be honest,” Harrison told BoxingScene.com regarding facing Charlo a third time. “I think after that fight I don’t think you’ll see Tony Harrison lace up a pair of gloves no more. So, it’s literally the only fight I want, the only fight that’s significant. If I can go out fighting him, for the legacy of my father, that’s the way I wanna go out.”

Ali Salaam, Harrison’s father and trainer, died from complications caused by COVID-19 in April 2020, just 3½ months after Harrison’s 11th-round knockout loss to Charlo in their second fight. Salaam, who was 59, worked his son’s corner for the last time the night Charlo regained the WBC 154-pound crown from him.

The 32-year-old Harrison has fought only twice since his loss to Charlo in December 2019 at Toyota Arena in Ontario, California.

His first fight following that devastating defeat resulted in a surprising split draw with stubborn underdog Bryant Perrella (17-3-2, 14 KOs) in April 2021 at Shrine Auditorium & Exposition Center in Los Angeles. Harrison bounced back from that subpar performance in his 12-rounder versus Perrella to thoroughly outbox Spanish contender Sergio Garcia (33-2, 14 KOs) in a 10-round fight that occurred last April 9 at Virgin Hotels Las Vegas.

“Climbing my way back up to a ranking,” Harrison said, “and going through people I had to go through to get the fight I wanted to get, that’s what I did.”

Detroit’s Harrison thought he would need to go through WBC interim champion Sebastian Fundora (20-0-1, 13 KOs) to get another crack at Houston’s Charlo (35-1-1, 19 KOs). Tszyu’s insistence on fighting for the WBO’s interim title once his January 28 fight with Charlo was postponed due to Charlo’s hand injury unpredictably placed Harrison in this position.

Tszyu is ranked number one by the WBO. The son of former junior welterweight champ Kostya Tszyu figured he would fight second-ranked Bakhram Murtazaliev for the WBO interim championship, but Russia’s Murtazaliev (21-0, 15 KOs), who is already the mandatory challenger for Charlo’s IBF belt, turned down that opportunity.

Harrison, who is ranked third by the WBO, jumped at the chance to battle Tszyu in Tszyu’s hometown.

“Once I beat Tim,” Harrison said, “it’s an easy deck of cards that I’m playing with to get that fight made or to show the people that [Charlo is] a fraud. I’m not even an Internet troll, but I will troll him all day if he decides not to take this fight. I fought my way back up to this. You know what I mean? … I will troll him all day. [Getting that third fight] is exactly why I chose the route that I chose.”

Charlo suffered his lone loss to Harrison in December 2018, when Harrison unanimously out-pointed him in their 12-round fight for Charlo’s WBC belt at Barclays Center in Brooklyn.

Their June 2019 rematch was postponed due to Harrison’s ankle injury. Their second fight was competitive as well, until Charlo dropped Harrison twice in the 11th round and stopped him after Harrison got up from the third overall knockdown he suffered in their rematch.

Harrison suspects Charlo, who has since become their division’s fully unified champion, will begrudgingly accept a third fight with him.

“To be honest, I don’t think it’s a fight he wants,” Harrison said. “But I don’t think he shies away from it, being from Houston and talking the way he talks, the way I talk. Me knowing Jermell and knowing the animosity he has towards me and the animosity I have towards him, and he’s a fighter at heart, I know for sure that’s a fight that he’s gonna take.”

Charlo will be part of Showtime’s broadcast team when the premium cable network televises Tszyu-Harrison live Saturday night in the United States (10:45 p.m. ET).

Keith Idec is a senior writer/columnist for BoxingScene.com. He can be reached on Twitter @Idecboxing.