Billy Joe Saunders is desperate to make a successful defence of his World Boxing Organisation (WBO) middleweight title against Willie Monroe Jr so he can set up a 'super fight' with either Gennady Golovkin or Saul 'Canelo' Alvarez.

The British boxer makes his second defence of the WBO belt against Monroe Jr of the United States in London on Saturday.

But a bigger prize is also at stake for Saunders and Monroe Jr as victory is expected to pave the way for a shot at the winner of Saturday's other world middleweight title fight between Golovkin and Alvarez.

Golovkin defends the division's three remaining major titles -- World Boxing Council, World Boxing Association and International Boxing Federation -- in Las Vegas, with his bout against Alvarez one of the most eagerly-anticipated boxing contests of recent years.

Facing either Alvarez or Golovkin is the opportunity Saunders has wanted since he won his title from Ireland's Andy Lee in December 2015.

But injuries and postponements have since restricted Saunders to a disappointing points win over Artur Akavov in December and he admits he became so disenchanted with boxing that he almost quit.

"When I was down I didn't want to box," Saunders told a press conference in London on Thursday.

"When you are down, you have to get yourself back up. I didn't want to box. I had a meeting with (promoter) Frank Warren and actually said I didn't want to fight any more. I wasn't getting what was coming to me."

Saunders, a 28-year-old from Hertfordshire, northwest of London, added: "I wanted to test myself. I went to the Olympic Games at 18, I won British, Commonwealth, European and world titles.

"I thought I've done all that, I don't need the money, I will get involved somewhere else.

"But I know I've got what it takes to beat Canelo or Golovkin. I'm not done until I test myself at the elite level. If I get beat by the better man, there's nothing you can do. I want to test myself at the elite level, against Canelo or Golovkin."

Saunders, who boasts a professional record of 24 wins, no defeats and 12 knockouts, is working with trainer Dominic Ingle for the first fight and has trained at his gyms in Sheffield, northern England, and the Spanish Canary Island of Fuerteventura, in preparation for Monroe.

"When I went to Sheffield, I got the hunger back, the desire back and I love boxing again," said Saunders.

He (Monroe Jr) is in for a big shock because there's a new and improved me and a happy fighter is a dangerous fighter," added Saunders as he compared his position to that of Floyd Mayweather, who recently defeated mixed martial arts specialist Conor McGregor in a boxing bout.

"McGregor was never going to beat Mayweather and Monroe is never going to beat me. I know I've got a multi-million pound fight in front of me.

"He (Monroe Jr) quit when he had all the belts in front of him before," said Saunders.