Manny Pacquiao wants a re-match with Floyd Mayweather, his trainer, Freddie Roach said on Wednesday at the press conference ahead of the Filipino's weekend bout with Australia's Jeff Horn.
But the 11-time world champion needs to dominate Horn in their 'Battle of Brisbane' bout is he is to get the fight, Roach said, because "with Mayweather you have to look good against an opponent, you have to be impressive".
"Jeff could derail us really badly. Manny is in a must-win situation. He wants a re-match with Mayweather," said Roach, who has trained 49 world champions.
Roach suggested that Pacquiao "might have to think about calling it a day" if he struggled to win or was beaten, saying "we are getting close to the end, I know", but he warned the Filipino veteran had shown signs of "the old Manny" in Brisbane -- knocking out two sparring partners, the first time he had done that in training for six years.
"We have to win this fight and we need to look good in this fight to get the bigger names interested.
"I expect Manny's best in this fight. I am looking for a big win here.
"A lot is riding on this. We want to go on to bigger and better things."
Pacquiao, meanwhile, said that he was not looking past the Horn bout but was keeping his fingers crossed for a Mayweather re-match.
"If there's a chance, why not? I'm willing," said Pacquiao, who has beaten Tim Bradley and Jessie Vargas on points since his Mayweather loss.
Roach said the 11-time world champion was ready for anything.
"We came here to win. We came here to be dominant. Whatever he brings we will be ready for. I think he is going to start quick because I think there's going to be an explosion right away. I expect him to be better than ever in this fight - that is what we are ready for."
Roach also said that Mayweather, who is currently preparing to fight MMA superstar Conor McGregor, had recently visited his gym, Freddie Roach's Wild Card Boxing, in Hollywood, Los Angeles.
Roach said that he was not sure whether Mayweather's visits were a sign that he wanted a re-match with Pacquiao after May 2015's "Fight of the Century", the biggest boxing event in history, having grossed more than $600 million worldwide, but he did not rule out the prospect.
"Maybe eventually he will come to the table," Roach said of a Mayweather re-match.
"Mayweather has come twice to my gym now. It's unusual. I said 'do you want to talk about Manny or anything like that?', and he said 'no, I just wanted to see the gym'. He said 'I might franchise these around the world', and I was like 'oh, ok'."